Let me just enter a word of caution for you about relying simply on eating side dishes while the rest of your family eats a full meal. That's a sure fire way to leave the dinner table still hungry and start to rely on lots of snacks to get full. You can quickly develop very poor eating habits that way. It's also a good way to overindulge in starchy side items, like potatoes, rice, and bread, again for the fullness factor.
It is not always the easiest thing in the world to become vegetarian, particularly if the other members of your household are not also vegetarian. I would never want anyone to tell you otherwise, have you discover that it is not, in fact, easy, and then get discouraged or think that *you* are the one doing something wrong.
Being the lone vegetarian may take more meal planning to plan meals where meat can be added, rather than the focus. Pasta is often as easy way to start, because, as someone already stated, 2 different sauces usually aren't too difficult to make. Or things like meat balls can be added for those who want to eat meat.
I would look at this not so much as the fact that you have to go to considerable effort to make something different for yourself, but as an opportunity to improve the eating habits of your whole family. You said your son medically cannot be a vegetarian. It's really a very rare medical condition that requires that people eat meat with every single meal, so that gives you leeway to prepare vegetarian meals at least some of the time. And the rest of the time, a compromise of meals where meat can be added seems in order.
I'd invest in a good cookbook if I were you. There are lots of recipes here and recommendations of good books here; I'm sure you can find something that will satisfy the taste buds of everyone in your family without having to sacrifice anyone's health, including your own.
Good luck, and welcome to the dark side.