What's the occasion? I'd make a whole bunch of different kinds of cookies, and a couple of cakes. Or, since you don't like to bake, you could ask people to bring dessert. You could candy some nuts-- see sage candied walnuts on this site. Make large trays of brownies (brownies from scratch are super easy) and cut them into small pieces, serve in muffin liners. (see chocolate fantasy brownie bites. That was their inspiration.). Do the same with a large tray of lemon bars. You could also put out good chocolate and candies such as caramels. Make a cheese tray. Hope this helps some.
You could make marzipan and then shape it into little fruits. You could make half of them with almonds, half with walnuts, and maybe even dip some in chocolate. No baking involved, serves the crowd, and it's made ahead.
Make Naniamo Bars (google it) - serve on a plate with a smear of raspberry sauce and piece of fresh fruit ... mandarin ?
I'm thinking along Barbara's line: a dessert buffet of different desserts that are relatively easy and no-fail, such as brownies. Also, a cookie platter is gorgeous. Make a basic chocolate and vanilla dough, use it to make cut-out cookies, then decorate them differently. A fruit and cheese platter might be very welcome given the sweets we're all eating in great quantity these days. The point is that you should enjoy the event as much as your guests, and not work yourself into a frazzle.
If baking stresses you out, go pot luck on it or find a good bakery or quality marker, where you can buy something delicious. On the other hand, there's no reason to think you can't bake if you can follow a recipe!!
One easy idea: Buy a loaf cake of some sort and make a trifle.
FruitsaladIt is a lot of cutting, but failproff. Serve with cream
You could do a few big pans of tiramisu - only involves 'assembling', not actual baking, is best made a day ahead, and a little goes a long way as it's so rich. I'd fill out the line-up with easy things like lemon bars, or brownies (add some dried cranberries/walnuts to make them seasonal.) Also, adding a board of cheeses with dried fruit, nuts, purchased quince paste, etc. and wheatmeal biscuits would offer an alternative to the sweet stuff and again, involves only assemblage.
make a whole bunch of mousse and divide it out into 75 mugs or ramekins before serving. it can be refirgerated up to four days so you can start cooking in advance. here is a good recipe http://www.davidlebovitz...
I've just had this wonderful Filipino fruit salad, thats easy to make and uses mostly pantry/fridge items - tinned fruit salad, Nata de coco (coconut jelly, available at Asian stores, apologies), cream cheese and condensed milk. See http://www.kitchenbutterfly.com/2012/12/17/filipino-fruit-salad-virtue-in-a-can/
For that big a crowd, I would recommend a texas sheet cake. Well, actually, the first thing I'd recommend is going to a bakery, but absent that option, two sheet cakes would work... Something along these lines: http://southernfood.about...
Yikes. I am not a baker either, but lazy Mary's lemon tart takes 0 effort and is really tasty. you could get a bunch of those disposable tin pie dishes. Lemon tart and chocolate sheet cake? Paired with a fruit salad and whipped cream? I would ask for help, though!