Tracey, I know just how you feel! We are also in a cat. 8 and would love to get upgraded!
As far as excursions go - on Grand Cayman we are going to the turtle farm and the beach. The turtle farm is a nice place and it's something that kids would enjoy (we have a 5 and 7 year old). In Cozumel we are planning on going to Chankanaab which sounds like a good place for kids (although we've never been there). Key West has a little aquarium that your DD may enjoy.
One of the reasons we like the Western itinerary so much, is that there are more things to do with kids in each of the ports than there are in the Eastern.
As far as excursions go - on Grand Cayman we are going to the turtle farm and the beach. The turtle farm is a nice place and it's something that kids would enjoy (we have a 5 and 7 year old). In Cozumel we are planning on going to Chankanaab which sounds like a good place for kids (although we've never been there). Key West has a little aquarium that your DD may enjoy.
One of the reasons we like the Western itinerary so much, is that there are more things to do with kids in each of the ports than there are in the Eastern.