Todd would like to have separate Apple IDs for his kids. Leo says users can have up to 5 Apple IDs per credit card, but only two Apple IDs per device. iTunes allows 10 devices with 5 computers. Todd will have to remember to deauthorize them when he stops using a device.
Leo also says that he can have as many iCloud accounts as he wants, and that's good for backing up photos to Photostream. Todd can have a separate iCloud account for Photostream and then a separate Apple ID for purchases and iMessages.