The beach was awesome. Beautiful sand and no seaweed at all. We also stayed at the Banyan Tree Mayakoba and both times we've been down there they seem to have a bit of a seaweed problem (which they manage ok).

Beach and pool service was good, but not excellent. Food and drink were fine, but you have to make somewhat of an effort to get attention which shouldn't be necessary at 47% occupancy.

There were a few families there, but it was mostly couples and the families that were there were mostly teenage kids and up.

ETA: I can't comment on beach chair comfort as we spent most of our time in chairs by the pool (the sand gets extremely hot), but there was never an issue getting a beach chair when we went even in the middle of the day. That may not be the case during busier times.