we stayed at blue bay grand esmeralda for 3 nights

should not be the same league as Riu, a lot cheaper i guess but we liked it.
 
Went there just before xmas, we rent a car ., if you can i highly recommand renting a car, giving you the freedom to explore the area at your own pace.  day1 we went to Tulum, and on the way back to the hotel we stopped by at akumal to snorkel at the yal ku lagoon ( so many fishes, even saw fish schooling) . day2 we went to PDC, the beach of course , and in the afternnon we went Pureto Morelos snorkeling to see the coral reef( a 2 hours tour).  we didn't go to the theme parks such as  xcaret,  xel ha... but could be a nice choice as you have 6 days there.  have fun..