Thanks! We have two kids under 4, and CPC had the kids club with buzzers for the parents (which we actually didn't use because our daughter was between baby & kid, so couldn't be left, and our son was too young). Prices for travel were fairly similar when we looked, actually. CPC has very reasonable wedding packages and Evelyn (the wedding coordinator) was awesome to work with, so that made it a better choice for us from that standpoint.
El Cid was recommended by a friend who went (on vacation) and by our photographer. It had a lot more options than CPC for weddings, too, so it depends what you are looking for!
I also liked it because my first name IS Marina If we didn't have the kids, we probably would have chosen it over CPC.
If you plan to do any of the day parks, the closer to Playa Del Carmen/Riviera Maya you are, the better. It was 70 miles from our resort to Xel-Ha/Tulum area, and that was a LONG bus ride.