I would suspect that even though the two of them enjoy each others company when Charles learns that his owner has left him in a strange home that he is going to be very uneasy. You may have a very stressed little boy on your hands.
Maggie doesn't have to go potty in the morning until 10:00am?
Wow. You have her trained!
Anyway, I hope things go well for all of you. Just be prepared if they don't settle down as soon as you would like. I'm sure you won't leave them alone together if they are still roughhousing.