Side to bring for birthday/Easter dinner for meat-and-potatoes father in law

If he's not very adventurous, homemade cole slaw is good. I use my cuisinart to finely shred the cabbage and grate the carrots. You can eyeball the amounts; this is how I've been making coleslaw for over 30 years. Super fresh juicy cabbage and sweet carrots are the trick, since it is so simple:

Finely shredded green cabbage
finely shredded red cabbage
Finely grated carrots
Good quality mayo (I use Hellmans/best Foods)
Salt, pepper, fresh or dried dill if you like
Raspberry vinegar or balsamic vinegar (not too much)

Toss together the veggies.
Mix the mayo with vinegar, salt, pepper, and dill.
Mix together. Add more mayo if necessary. It should be somewhat creamy.
Best to add the mayo within a few hours of serving. It tastes good the next day, but loses its creaminess.

The other thing I like to serve for less adventurous eaters is a big mixed greens salad with some red lettuces and perhaps radicchio in it, chunks of fresh pink grapefruit, thinly sliced fennel, minced parsley and fennel fronds, vinaigrette with less acid than usual (because of the grapefruits -- they will give off juice), and a sprinkling of finely grated parmesan or Romano or asiago cheese.

Or, roast a whole lot of asparagus with olive oil, salt, and pepper. Squeeze lemon or orange over it when it's done.

(I like to keep it super easy when I'm hauling food to someone else's house!)

What about a slightly unusual salad like: http://www.food52.com/recipes/11674_shaved_asparagus_and_mint_salad or http://www.food52.com/recipes/16471_italian_celery_and_mushroom_salad
Or a "normal" vegetable side dish: http://www.food52.com/recipes/9835_glazed_carrots_with_braised_bibb_lettuce or http://www.food52.com/recipes/4023_absurdly_addictive_asparagus