Channunkaab Park is still closed -ruined by the hurricane, keep checking with your TA or here for updates.
If your husband can float with a life vest on then he can snorkel the reefs off Cozumel. We snorkeled Palencaar Reef - amazing., there is this slight current that ever so gently pushes you along, you don' even have to kick your fins to move- maybe something to consider, depending how comfortable he is in the water.
At this point the best place for information on what beachs are open and what they have to offer would be from the Cozumel Tourism board. I don't know the web site off hand, i am sure you could google it and find out.
Mr. Sancho's is a great beach - if it is open.