If you don't have the Wii system, you need to get that first; I think it's around $199 now. When we bought our Wii Fit package to go with it, it was $99. So it is a pretty significant investment, but it's more flexible than a piece of exercise equipmnt because you (or your kids) can also play recreational games on the game system. There are different types of exercises you can choose from, if I remember right: balance, yoga, cardio, and strength. Choosing what you want to do, you are on your own. However, they have come out with some games now for the Wii that put you on a program and tell you what exercises to do each day, as well as give you a chance to log in your food. My husband is just getting started with one of those.
I think the most important thing is to just do something, anything, to get started. Good luck to you!