Great. Our 6 year old liked it as a 5 and 6 year old. Lots of life jackets, floating down the river. Doing zip lines w dad, etc. My kids are likely tougher than yours though. Ha, i kid, i kid.
If you do Xel Ha I strongly recommend buying the picture package so you can take as many pics as you want all day and they give you a link for them at the end of the day. So worth it.
The manatee swim made me dad of the year too! Well at least until I dropped them off at grandmas for a week and went and got naked at Desire and partied like it was 1999 at TTR and did some bad things to bad people ha
We used Altournative tours for a tour of Coba and a few other stops. They planned on smaller more active groups when we used them. Two tours were great.
The best excursion other than a Boobs Cruise is a second Boobs Cruise! Each one is different. We have done some of the above mentioned, but realized that we kept wishing we were back at TTR and haven't done any more for the last 3 years. We save them for cruises and other less entertaining destinations.
We did xplore, it was fun we also got the picture package they gave us a key with all the photos on the way out. I am not sure how good it would be for a preteen, we did see kids but not that many compared to the adults and teens. I think 8 of us went private tour (EntertainmentPlus) ~$120pp We also did a Day trip to Ek Balam, with a cenote stop and a couple hours in a town/city Valladolid. It was a private tour booked with EntertainmentPlus (Same as USA Transfers, using the CCC referral code) . It was a good day but after the Tour price, lunch, guide at Ek Balam it probably ended up around $600 for 2 for the day. Price per person drops pretty quick if you find other people to go with.