Cap't Morgans is $159 per cabana (low season), not per person.
Lynn - Personally I would not recommend splitting the trip up into 2 hotels on AC. It would basically be the same experience with a few miles and "hotel ambiance" difference. If you want to split up the trip why not part on AC and part on the mainland (which is where you will be going for the ruins & cave tubing anyhow)? Or if you want all beach accommodations, how about a few nights on AC and a few nights in Placencia or Hopkins/Dangriga area? There are some ruins near Placencia/Hopkins and the cave tubing can be done as a day trip from either place.