Young kids seem to gravitate to the Wii. If you want to pick amongst the 3, one way to choose is get one that most of his friends have. That'll make it easier to share games (and cost).

That being said, I'm with you regarding the 'iffiness' of introducing kids to video games. I have the DS, PSP, Wii, Gamecube, and PS3. But I'm the major player because I know how addictive these can be and the last thing I want is a battle w/ video games and my kids. I've let my kids play Wii but only turn it on w/ a pre-agreed time limit so that there's not fight to turn it off.

My 6 yr old daughter also asks me for her own DS often. I told her she can get one when she can explain to me what it is. She doesn't really know because her group of friends don't play it and I don't play it in front of her often. Don't know how long I can keep that going though...