Oooo I think the best thing would be to serve something brunch-ish? You could do slices of frittatas or quiche instead of sandwiches (both are relatively inexpensive to make, based on the ingredients, since they use a lot of eggs/potatos), and then also have muffins or scones (again, usually relatively inexpensive).
The Smitten Kitchen cookbook also has a really great potato/feta/scallion/bacon frittata recipe that I could forward along if you'd like!