How about a fruit salad? All that's involved is picking the fruit from the store, washing and chopping, and putting it in a bowl. Just get some delicious looking fresh fruit (you could even get berries from the local farmer's market and do a berry salad) - easy, quick, and hard to mess up. If you're going to cut up apples, put a little lemon juice on them to keep them from going brown.
If you want a little more direction on a fruit salad, check out this section of allrecipes: allrecipes.com//Recipes/salad/fruit-salads
PS - try to relax a little! No one's going to judge you as a person on how well you make a plate of food for an event (I never have, and I am pretty sure I don't know anyone else who has either)- they will be talking with you and getting to know you - and learning why your boyfriend already knows you're so awesome and such a great catch!