The key to making and serving a 3 course meal is preparation and timing. you don't want to be slaving in the kitchen hurrying around while your guests are there, most of the food should be prepared ahead of time or almost ready to go.
Asian is great, you can make sushi ahead of time, prepare dumplings to be steamed ahead of time etc.
another option is italian, its versatile, familiar to omni's and can be done with ease for a 3 course meal. maybe something like a bruschetta appetizer with a side salad, veggie lasagna or baked pasta dish main course, and granita for dessert. granita is a kind of icee frozen fruit dessert, really easy to make with pretty much any fruit in season.