The short answer is don't feed them ham. But, what can you do? Well, it is really not that complicated. Let's start at the beginning.
If you are having appetizers, don't just have cocktail wieners. Cheese and crackers or deviled eggs are quick crowd pleasers. You can also start with a salad, but don't stop there.
Side dishes can work for meat eaters and vegetarians alike - think baked mac and cheese, green peas, mashed potatoes. Just be sure not to use chicken stock or ham hock or any other meat product in your recipes. I live in the South and pretty much every green vegetable is made with meat. The recipes of our grandmothers all start with add some bacon to the pan. If you don't believe me watch Cooking with the Neeley's on the Food Network. They are fellow Memphians and it never fails they find a way to put meat in everything! Don't do it if you are having a vegetarian over. Use other spices or vegetable stock (it is on the shelf right next to the chicken stock) to season your sides. Also, rolls are a hit with carnivores and vegetarians. This time of year I get a craving for Sister Shurbert's rolls, but any kind will do.
But, what about the main dish? I know you are thinking your meal wouldn't be complete without the ham. Most vegetarian won't necessarily feel that way. First, realize if they have several sides you may not need one. Secondly, you can always ask your vegetarian for their favorite recipe and try to make it. Or, you can even ask if they could bring it. We really don't mind cooking if it means we will have something to eat! Some of my suggestions would include spinach patties (think crab cakes but with spinach instead) or a cheese quiche (this is great if you are doing brunch or dinner).
Finally, don't forget dessert! A fresh fruit pie would be a wonderful ending to a satisfying meal or even a chocolate bunny. In the end, remember not to stress yourself out about this. The point of the holiday is to share it together - it is not about what is on your plate. Happy Easter!