Welcome Emilie! Pasta dishes seem to always go over well with larger gatherings. You might want to check out the pasta forum for some ideas. I'd serve it with a salad and bread. For dessert I'd probably buy an angel food cake and make a berry topping to serve with it.
Here are some ideas....note the serving sizes and adjust:
Salad Dressing: I just have an assortment to accomodate. And I'd buy prepackaged salad.....I love the Spring Salad Blend. The Italian Blend is really good too.
Angel Food Cake with Berries:
Buying the salad prepackaged and a store bought angel food cake will save you a lot of cooking time.
Hope this helps!