Patrick would like to set up everyone in the family with Apple IDs, but he can't get everyone on the same account. Leo says that according to the chatroom, he can only use three Apple IDs per credit card. So he'll have to have another credit card for the rest. One other option, according to Leo, is to go to his bank and have them generate dedicated credit card numbers that are linked to his account and can only be used with iTunes. Or, better yet, set up each ID with a separate iTunes gift card. Then fix it to where they can only be used with the gift card. That way his credit card isn't saved to the account.
It also won't allow for attaching more than three Apple IDs to the Calendar, though. Leo says that is a limitation to the Apple OS. He recommends using Google Calendar to share and sync. Then Google will push it down to the Mac automagically.