iMessages on same Apple Account but Multiple Devices?

So my wife had an iphone to start so she has her apple account. Well we bought two ipod touches for the kids and obviously since they were under age we set them up under her same apple account. The nice thing is when we buy a game on one phone we can install it on all 3 devices at no additional charges. But now that ios5 has came out I have installed it on there devices and if one of the kids sends a message to me (not on the same apple account) or even to there mom they will come from her name and it shows up as she sent it as well as when she responds it goes out to everyone. So its sending/receiving on all 3 devices now.

Anybody know how to fix this? When I go to iMessages settings there is a caller id but it asks for another apple account and I think we will have to sign in and sign out if we want to download apps vs use iMessages? We just want the kids to be able to message us without it going to everybody but dont want seperate apple accounts for the app/billing issue. Thoughts?