Had to split my post:
Maybe you could trade who 'gets' to go with Mommy when you leave the room. As with ABQmom, I see this approach as potentially causing more jealousy in an already adversarial relationship. No doubt your kids have rivalry...they have such little stand in the world at large that they're not about to give away their foothold in the family. My kids are similar in age to yours...I also don't give them a lot unsupervised time because my DD2 is, understandably, impulsive and yet my DS5 lacks the maturity to understand this. There is daily smacking, shoving and tears ...and they do really love each other!
