I would do a salad bar.
Seriously. Grill a few chicken breasts (with bones, so it isn't dry), put them in foil in your warming drawer maybe and when you are ready to serve, slice the meat as if for fajitas, so people can put the amount they desire on top of their salad.
Mix of spring mix and fresh romaine lettuces torn in a big bowl.
Sliced (in halves) cherry or grape tomatoes.
Sliced black olives.
Cucumbers (I like to slice rounds and then quarter those).
Red onion, diced, but not too small.
Red bell pepper, slivers.
Matchstick carrot slivers.
Shredded cheddar cheese.
Small cubes of some other specialty type cheese (I like to buy a block and cut slices, then cut the slices into smaller cubes).
Sunflower seeds.
Maybe some carmelized sliced almonds.
You can prep it ALL in advance. Then just set out the items in individual serving bowls in a buffet line, with the chicken and a variety of dressings at the end. The kids can make a plate (and not mix their food items if they don't like them mixed--mine did it that way for a long time), and adults can use what they like and skip what they don't.
It's a VERY healthy way to eat, and lets people cater to their own tastes. It's plenty filling, and clean up is easy.
Serve it with some fresh bread. Coffee and cookies (which you can prep in advance also) for dessert. Or if you want to be more elaborate, but not complicated... bake a simple pound cake, and wash, slice some fresh strawberries. Mix some sugar and a spoonful of water into the strawberries a few hours in advance (keep in the fridge). When it's dessert time, slice the cake, spoon some strawberries on the slice, then top with reddi whip and/or drizzle some chocolate syrup on top. Never fails to make people happy, and so simple and easy. It also keeps easy (the cake stores on the counter, and the strawberries don't take much room in the fridge).
Whatever you decide to make, don't stress over it being perfect or served just so... relax. People like feeling welcome, and enjoyed. Not stress inducing. :)
