When I was a kid, my parents lived about a quarter mile apart and were able to 50/50 custody for a while. I lived at one place for a week, then moved to the other for a week (sunday-sunday). I hated it, I called it "ping pong" and I never felt stable. I always felt more secure living with mom OR dad rather than mom AND dad (and seeing the other parent as much as possible, of course).
Whatever you end up doing, talk to your kids about it and see what THEY think. I realize they're young and don't know what's best for themselves at this point, but if they're not feeling stable and secure, they're going to suffer.
