Twinglez: Here's another idea for PV that might work well for your DD who wants to stay on the ship. About a five minute walk from the port is a resort called the Krystal. They let cruise ship passengers use their facilities for free. They have a great, meandering pool with fountains, bridges you can swim under, swim up bars, volleyball and basketball and a separate pool with a (small) water slide. It's right on the beach, so you can have access to both. (We never made it to the beach because we did an excursion that day and only had about an hour to spare for the Krystal, so I can't tell you how good the beach is.) This way, if you want to take DD back to the ship, it's right there.
Just a thought, something I learned on our recent trip: What DS (10) really wanted to do was stay in the room and watch movies and order room service on sea days, not spend as much time at the kids club. Unfortunately, I didn't let him do too much of that and I regret now that I didn't compromise a little bit more. Like a friend later told me, it was his vacation too. My point is, I guess, that I had expectations about how he should spend his time, but it wasn't what he would have enjoyed most. That may not work for you in your situation, but it was eye-opening for me to see that by forcing him to "have fun", he wasn't, really. Not that I would let him hang out in the room all the time, or wander around by himself, or let him just blow off family things, just that next time I will try to accommodate and be a little bit more understanding about what he wants to do, (even if I don't think it's necessarily the best use of his time).
BTW--We did the canopy tour, booked through shore excursions, and the whole family loved it, even DS. I highly recommend it. Unfortunately, your 5yo twins couldn't do this one. In Mazatlan we did Stone Island. Nice beach, lots of fun, a few jellies. In Cabo we were on our own (kayak tour got cancelled due to high waves) and went shopping. DS stayed on the ship for that one and had much more fun than shopping with the adults.
Crowncaster: You can look for Los Veranos Canopy Tours on line. It's likely the independent canopy tour that TootyJane was talking about. Several members of our group did this one and were really happy with it. You can email the owner (can't remember her name right now) and she will give you all the information about which taxi to use, where to meet, how much it should cost, what to wear, etc. My friends' group got muddy from head to toe, so bring old clothes to wear on that one!
.....Tooty Jane is right about wearing something bright/noticable. There are some distance shots on the DVD and clothing is about the only identifier. But, make sure it's something old and/or cheap. Most likely it will not come clean!!! We thought it was an awesome excursion.
