If they are all yours, that's fine. If different people use them, you should have different ID'S for each. They can still share the same iTunes ID. But iCloud,iMessage and Facetime ID's should be your own. Also, if they share the same iCloud ID, they have to share the same 5 free gb of iCloud storage. Separate ID'S and each device has it's own 5 free gb of storage.