How many Apple IDs should your family have? — Apple News, Tips and Reviews: "With your family’s iTunes purchases under control, and the core features of iCloud storage taken care of, there is one particular feature of iOS 5 that can be set separately from a device’s primary iCloud account. When it comes to locating each of your family’s devices, do not rely solely on the Find My Friends app to locate their position. Create a common family iCloud account and configure each device to use this account in the Mail, Contacts, Calendars settings. In fact, you can even create this iCloud account without creating a new Apple email address. This family iCloud account’s sole purpose will be to keep track of all of your Apple devices."
Wow - that can get a little confusing; but it is possible to set up a pretty flexible combination of ApplieIDs on your devices.