If you want to keep it simple, I've used something like this http://www.turtlewax.com/main.taf?p=2,1,4,16
. You spray it on, let it sit for a few seconds or minutes and scrub it with the attachment on the can. They work really well at removing stains.
If you're seats are stained and a little grimy from the kids dropping juice and snacks, then maybe you might consider steam cleaning them. Here where I live they rent the Dirt Devil Carpet Cleaner machines at the supermarket. They have an attachment with a smaller head. I would definately test it on a small piece first and use very little of the cleaning solution just to make sure your seats don't get messed up.
If you're not too excited about doing it yourself, you could go to a auto detailer (not a car wash) that does seat and carpet cleaning with a steam machine.