We love the Peruvian Ceviche at My Paradise Bar, just about 10 minutes walk along the beach. Unico Bar also has good food, and El Merkadito is great too. There are a few really fun nice restaurants in Puerto Morelos.
www.vivapuertomorelos.com is good for getting the lay of the land if you are feeling like heading into town.
Puerto Morelos is a nice town and the pescado frito is not to be missed - fresh catch of the day, battered and fried, .. yum!!
Enjoy your honeymoon!