My family and I travel to all-inclusive resorts often and have never had a bad Riu experience. Riu Dunamar was no different. My family of 9 (including 2 kids, 12 and 9) spent a week there over spring break and it was wonderful.
Pros: the grounds were impeccably maintained, people were hard at work cleaning/maintaining at all times. Employees were friendly and helpful (special shout out to Willy at the swim up bar and Elizabeth at the breakfast buffet). The beach was AMAZING; free of seaweed, clean, and ocean was swimmable. The pools were clean and warm. The water park was a huge hit for my kids and I felt safe sending them there. The food was pretty good (I'm a picky but not fancy eater) and I didn't have any trouble finding something to eat for any meal. The drinks were pretty standard, nothing fancy but I couldn't complain.
Cons: chairs by the pool were completely claimed before 8am. Beds in the double room are SMALL, like smaller than a full size small. With 2 kids, we were lucky to get a room facing the outside of the resort, as I can see if you face the interior of the resort the sounds from the show and guests would be really loud into the night. There were a lot of unruly spring breakers but the staff was pretty good at handling them.
All in all, this might be one of my favorite Riu resorts and I would not hesitate to go back.