Kind of depends what your non-diving interests are (as a couple). Playa del Carmen area is nice. A rental car for the week and you're set! Golf of course if you're into that. Lots of history to explore @ Tulum, Chichen Itza, Coba, etc. Shopping in Playa and Cancun. Outdoor adventure @ Sian Ka'an, Xel Ha, Chankanab and a variety of EcoTours. Great snorkeling right off the beach @ Akumal ( makes a nice day trip when combined with Tulum and a cenote tour and other activities @ Hidden Worlds) and not even bad off Coco Beach on the North end of town as well as some of the park areas mentioned above. Guided tours (both snorkel and open circuit) of a number of cenote's which are not to be missed. Good restaurants. An easy ferry trip to Coz for more great diving while the SO explores island shopping or sights. On the other hand, if you just want to hang around a big resort -that still has plenty of activities but of a totally different type than the get out and explore kind of thing that we enjoy- and still want some good diving, my brother and sister-in-law really liked the Beaches Turks and Caicos resort and the diving's very good.
Gary