Kid-friendly, tasty, simple-to-make Christmas dessert?

I wanted to thank all of you again for all your helpful suggestions. We ended up doing simple cut-out butter cookies, which my nephew helped make and helped decorate. He had so much fun! and he talked about it for days and days - it made a real impression on him. And for dessert I ended up cutting a simple gingerbread-style cake into small houses and decorating them, like this: http://www.kingarthurflour.com/recipes/gingerbread-house-cakes-recipe
These came out super-cute and were a huge hit with young and old alike and they were very simple to do. I did modify the gingerbread recipe quite a bit because I don't actually like gingerbread but other than that, super easy and again, lots of fun for my nephew to help bake and decorate.
So I owe you guys many, many thanks - it was a big success and really helped make my family's Christmas celebration. Thanks again!

I make cut out sugar cookies, using fun cutters. I make several colors of frosting and my young grandchildren do all the decorating. Everything is ready to go with piping bags and sprinkles. They love it.

Nope - we're Italian, we start 'em in the kitchen very young! We were all "helping" make cookies at that age, not to mention things like gnocchi, and we loved it. It's very much a hands on family event and everyone is included. And of course we're only talking about the fun (and safe) stuff like decorating, not actually cooking anything. Thanks for the suggestions folks, keep 'em coming. Great ideas!

Three? Isn't that pretty young for making food? Why not make some playdough and let him explore making fun projects that don't have to be cooked. Leave the food and the stress to the cooks (including yourself when you arrive).

Make a nice chocolate mousse and bring different toppings; berries, crushed candy canes,chocolate chips, peanut butter chips, mini gummies, etc... Our kids and adults love it.

Gingerbread houses can be really easy. They have kits with necessary ingredients. You can add extra fancy ones if you want. Using frosting to glue the frame together can be difficult so we just hot glue that so it is sturdy. Then use frosting for all of the decorations which are the things the kids will want to eat. They really won't want to eat the house.

I second the suggestion of chocolate icebox cake. Chocolate wafers spread with whipped cream. Or brownies. Joanne Chang's from the Flour baking book are really good. Or the recipe on the Ghirardelli Ground Chocolate canister--not quite as rich but super-easy. Serve with vanilla ice cream and you're golden. Candy cane optional.

how about traditional trifle---so easy and a beautiful presentation. My mom always used Bird's custard---here's the closest recipe that I could find--http://www.theguardian.com/lifeandstyle/wordofmouth/2011/dec/22/how-to-make-perfect-trifle

I'm so glad I posted this here because you guys are so creative! I never would have thought of all these options on my own. Thanks so much!
I adore the gingerbread house idea but wow! that seems like a daunting project - anyone have any experience with a simplified version?
And yes, I'm going to do some testing over the coming weeks and I'll definitely let you know what I end up with. In the meantime, if you've got an idea, please share!

June's idea is great, adding to it what if you premade the gingerbread house and assembled it together. :)

Peppermint bark is delicious, and very easy to make and transport. You wouldn't want to expose it to too much heat in transit, since the base is chocolate.

I like petitbleu's suggestion of a peanut butter chocolate pie. My eight year old daughter has requested one for Christmas or New Year's this year. It's such a festive dessert, guaranteed to make everyone smile. It can be made ahead, so long as there is refrigerator (or freezer) space. And your nephew can decorate the top with sprinkles, chocolate chips or melted chocolate. I like five&spice's recipe: http://fiveandspice.com/2011/08/12/a-peanut-butter-pie-for-mikey/

It is a tradition in my husband's family to make a pecan torte for Christmas dessert. This is basically layers of meringue made with egg whites, sugar and crushed pecans. The filling and frosting are one and the same -- more crushed pecans and whipped cream. It is a fun, celebratory, child friendly dessert. It can be made a day ahead but does need to be stored in the refrigerator. If you'd like the recipe, please message me.

Let us all know what you decide!

You could make cream puffs - make the puffs up ahead of time (lightweight to carry!) and fill them with pudding mixed with whipped cream before dinner. You could do several flavors, several sizes and pile them all on a platter like croquembouche (sp?).

I have fond memories of my Mom decorating cupcakes. You could make mini ones and let the kids spread the frosting and decorate with candies.

I would make a simple pie, such as chocolate cream (using a simple crumb crust and a basic chocolate pudding, topped with whipped cream) or peanut butter (provided no one's allergic). As a kid, I always loved pie. Or you could even just make chocolate pudding and top with whipped cream and crushed peppermint candies.

Ooooh, great ideas, keep them coming! We already plan to make roll-out cookies with my nephew. In fact, I'm bringing down my mother's ridiculously comprehensive collection of holiday cookie cutters so that should be fun for him. What I'm looking for is a centerpiece dessert (we're a big family with a serious sweet tooth so just cookies won't be enough) to make in lieu of a cake. Love the icebox cake idea because he's at that age where he loves to help so I may do a test run on that this weekend (since I've never made one). Plus, the kid's got a thing for whipped cream - he stole it off everyone's plate this past Thanksgiving so I bet he'll love that.
Thanks again for your help and do keep the ideas coming in - I've got a few weeks to plan so I'm very interested in all suggestions. Plus, I made a beautiful pumpkin pie for Thanksgiving but then promptly dropped it all over the floor and ended up having to bring a store-bought pie - so I've got to redeem myself!
Thanks again!

Quick, easy, & delicious: get (or make ahead) great chocolate chip cookies (the thin & crispy kind) and chocolate pudding. Layer them alternately in a trifle dish (a bowl will work too!) and put it in the fridge while you eat dinner. Then scoop it out into bowls - the cookies soak up a bit of the pudding, and it's awesome! This can also be made gluten-free by using gluten-free cookies. I've made this for holidays when I've needed a quick no-bake dessert, and it's a big hit with everyone.

You could make truffles or brazilian brigadeiros, put them on sticks like cakepops and decorate together. Food & Wine had a nice and simple brigadeiro recipe http://www.foodandwine.com/recipes/brazilian-rich-chocolate-truffles

Chocolate icebox cake made with chocolate wafers and whipped cream. No baking required! Shape into holiday themes like a yule log or snowman. Decorate with candy. Easy project for little kids and just about everyone I loves this cake.

Cookies and fudge are great ideas. Or, just pick up his favorite flavors of ice cream when you arrive, and let him concoct his own sundae with red and green M&M's, crushed peppermint sticks, etc. (easy to pack and bring on bus.) All you'd need to do in situ is make a quick chocolate sauce and whip some cream - 15 minutes of kitchen time, tops.

What about fudge? Fairly fast to make, just a few ingredients, good for kids because you can cut it into mini-mouth sized pieces - and you can customize however you want! I love to add crushed peppermint sticks to mine to make it fun looking :-)

If you have a bit of time before you go, cut out cookies -- both gingerbread and sugar -- are big hits with most kids. And they'd travel easily in a box or tin with waxed paper.