Oh, but there are so many good period dishes for something like this!
Quiches, or as they called them then, "Ember Day Tarts." Can be made vegetarian. Use any quiche recipe you like; my favorite is cheese and mushrooms. Expect each quiche to serve 8 slices; plan enough for 2 slices per person.
A big beautiful salad of spring greens is very similar to period "sallet," especially if you snip some chives over the top (they used a lot of savory greens in salads), toss with olive oil and vinegar dressing, and decorate with edible flower petals.
Sliced cold roast meats (not lunchmeat from the deli, but some nice roasted turkey breasts and beef roasts) served with a choice of sauces, like mustard and cameline (a sweet sauce made from raisins and meat drippings, and thickened with breadcrumbs). I know turkey isn't period, but slicing roast chicken is a pain.
Go online to Cariadoc's Miscellany (www.pbm.com/~lindahl/cariadoc/miscellany.html
) for tons and tons of good period food ideas and tested recipes that people like. As a bonus, Cariadoc is a former King of the Middle, so using his site would be even more appropriate!
Best of luck with your feast!