Grand Oasis Palm is a good resort for families in my opinion. Just for clarity, we stayed in July 2014. If you are thinking about a nice economic stay in Cancun, this place will serve you well. It is not a 5 star hotel, but it is a nice vacation for the family, with good food, drinks, pools, etc.
We loved the sushi bar, and spent many late lunches there. The buffet was good, and I personally really enjoyed the a la Carte restaurants, although my wife was so-so on them. The sign-in process was a pain, and they did try to charge us for things we did not use in the mini-bar, but since we were forewarned, we took pictures when we arrived, and again when the bill came, and were able to dispute that quickly. We enjoyed having the Capitan Hook boat at the edge of our property, and where able to walk around outside to a few quick excursions including the local open air Catholic Church down the street.
My girls loved the pool and the shows were fun and impressive. Our family particularly liked the circus. The Mariachi bands on resort brought the culture to you, and we were all happy with the drink selections (although we are not serious drinkers) and lines to the bar were reasonable. The beach was okay. The waves are shallow and not many shells, but in general the kids had fun in the water and it was still a very enjoyable experience.
Service was okay. The workers did seems stressed and not attentive, but they did work hard. I was really impressed by the sushi crew, and though things were slow, it was more of a management issue than the workers themselves. They busted their butts to get things done.
I think the thing to remember is that it is an economic vacation, not a cheap vacation. The rooms and food and entertainment were all good to above average. They were not five star, but no one going here is paying for five star. In my opinion, five star resorts are too expensive, and unless you are used to that on all your previous trips, you will have a great vacation without breaking the bank.