Are you using iMessage or regular SMS messaging?
iMessage would (optimally) require one Apple ID per device; so if you have the same Apple ID on your wife's phone and your daughter's iPod touch, this can cause problems in receiving/sending duplicate messages. I think that seems to be the problem at hand; so create an Apple ID for each device/person.
This shouldn't be required, but go ahead and go to Settings<General<Reset<Reset All Settings (this won't erase content)<Yes on each device. You will now reboot and go to the iOS 5 setup screen, where each device can setup their own Apple ID.
Very sorry to hear about your Apple store experience.