First, you'll love Orion - we chartered her before and loved it! A few observations,
1. You might be able to drop your check out captain at Norman and he can take a ferry back to TMM (we've done this before)
2. Tues, you might consider getting up early and off your mooring ball; motor over to the Indians and grab a ball for some early morning snorkeling. Some folks might stay on the boat & get breakfast together while others choose to snorkel. It's great snorkeling.
3. I'd vote for a night in CGB - lots of activity and a great place for the kids to play
4. Monkey Point is a great snorkel stop and always one of our favorites. We usually get there before Noon to get a ball - there are only a few in there.
5. For your last night, TMM might require that you stay in the marina your last night in order for them to insure that you get in a taxi and to the 10:00 am ferry to STT. The check out procedure takes some time.

Looks like a great week on the water!