Light, compact, fun to shoot,and reasonably powerfull, are what I'm looking for.
Parker Enforcer. For a kid I would go Enforcer with Hawke Mulit-rec, in fact I just did. It is really light and is compact becasue of compound limbs. 300FPS at 160 draw is plenty (you are likely going to have to cock anyone you get for a couple years)
We really like ours so far...my son (13) wants to carry it for gobbler in fact over a shotgun. He got a deer with our Tornado last year, and is very accruate with it. Although better made and a little more compact, it is quite a bit heavier and I see no accuracy advantage at least in normal bow range over the Enforcer.
They are all fun to shoot.
You will get many responses here but stay focused on the kids...my kids hunting is why we got into crossbows, but I love shooting them too...ENJOY DIVING IN and let "arrowhead" set you up, takes all the hit and miss out of it.
My 6 year old son is not ready to hunt yet (hope he does not read this
), but my daughter is 12 and going out this year for the first time, we got some shooting to do there , but 2010 is going to be a good year.