We just got back from a Western Cruise as well. I did a lot of research before leaving because I too had heard that Xcaret had fake ruins as well (from various people that had been) and I wanted authentic ruins. After looking into it, I found that there are some genuine remains at Xcaret, like cenotes which are sinkholes. Not a lot of authentic ruins though like other sites. If you read their website closely, which is posted above. They are careful with their choice of words, but read carefully. Straight from Xcaret's website (under culture) it says "In our Park you will discover the vestiges of the rich cultural heritage that the Maya, these incredible mathematicians, astronomers and architects left to mankind." What does Vestige actually mean?? It means a trace or visible evidence of something that is no longer present or no longer in existence or a very slight trace of remains. Also be careful with Wikipedia as a source. It is written by volunteer people and we have encountered a lot of misinformation from this site (learned the hard way while on vacation). Just what I have discovered. If you aren't going just for the ruins though, Xcaret is suppose to be an awesome place (lots to do like snorkeling, etc.) My mother wanted to see ruins though so we decided against Xcaret.
We opted for the Mayan Ruins and Beach Tour as well. We had two younger daughters and thought Tulum would be too much. Our guide even told us while there that Xcaret was not real . I agree with the pp about our tour. We didn't eat the buffet though but did enjoy the beach even though it was crowded (got lucky and found empty chairs together right next to the water). Plus we did get one free drink per person at the beach (beer, margarita, soda, etc).
RLP817- we must have been on the exact same tour, we were there on the 23rd of March. My two daughters (plus another girl) were asked to walk up part of the ruins by Caesar our guide.