There is no way that 4 hours is enough time to do everything. If you go on the tour of the ruins and butterfly farm that is an hour by itself. If you do the lagoon that is another hour. This leaves you 2 hours to walk around this huge park and eat. Maybe if you skip the tour you might make most of the big stuff, but part of the reason for going to Xcaret is to see the caverns and stuff. Trust me on this one. Do NOT go in the caverns without a guid. They are very long and winding and we ran into several people that were lost.
If you want to go, go because it was a lot of fun for myself and my husband. My daughter complained the entire time we were on the tour but loved the lagoon. We really wanted to hit the aquarium but didn't have time. If you go, take pictures so I can pretend we made it.