My choice would be Barcelo - better beach,closer to Tulum and Coba ruins and in some opinions better food. Unless it has changed since 2005 not all restaurants @ the Ibero* are a/c - uncertain about the Pallidum but I don't think all are a/c there either. I would save the $648 for spending $$ or towards my next trip down - and unless you have a different experience than most you will be going again, and again, and again.
Have a great trip - I'm at the Grand Riveria Princess mid-July with 3 teens myself.