i agree with Jen. All you indoor cats are bonded and as long as they stay together, the younger ones will pull the older ones along and help with the transition. I wouldn't worry about it.

The porch cats? Would the rescue group which helps you with them now take over their care?

A friend of mine has a feral colony just now that we are working to relocate. The caretaker died unexpectedly; she was found dead in her home in mid October. Her only living relative is her deceased husband's brother. He has made it clear to us that the cats must go. We will trap them, relocate them, keep them confined for 2 weeks in the new location so they get used to the sounds, sights and smells, then release them. The hard part is not trapping them; it is finding a place where they can go. We are working on it.