We'll expect a trip report with lots of pictures, Cliff.
The next time we are able to go to the RM, we also will be going with a 3 year old (and his big sister) so I will really want to read your report.
Puerto Aventuras would be a little closer to Aktun Chen, which also has cute animals for your daughter to look at. I remember back in 2003 when we were there, someone brought their pretty-close-to-newborn baby on the cave tour.
Playa would be closer to Crococun, if Crococun ever reopened?