Ahoy, Karen!
When we were getting ready for our very first Disney Cruise Line vacation six years ago, I had it in my mind that we would surprise our daughters with it on Christmas morning. Like you, I struggled with exactly how to do it. My girls were six and nine at the time, so it would have to be something relatively obvious so that they would "get" it right away.
After much deliberation, I decided to get some helium balloons. I attached the words "Disney Cruise January 16" to the balloons, anchored them to the bottom of a large box, and wrapped the box carefully. I made sure that all the girls would have to do was untie the ribbon and lift the lid and the balloons would fly up. It was HUGE!
I did this all on Christmas Eve. So, we all got up on Christmas morning and went downstairs to open gifts. The girls kept staring at that huge box with no tag on it. Finally, I told them it was from us, and that they could open it. They did, and the balloons did their job, flying up into the air. My daughters read the balloons' words and started jumping around! They were thrilled. I also made them a countdown chain that we hung up and took off a link each day until the cruise. Since we were cruising just three weeks later, it was great!
As far as fun family beaches in Cozumel, I have heard wonderful things about the
Caves Caverns and Paradise Lagoon Port Adventure. But, I will warn you, it travels to the mainland via ferry, and the trip is rough (lots of people were sick on the ferry on my last cruise to Cozumel).
I hope you have a wonderful time surprising your daughters! Please visit us here at the Disney Parks Moms Panel with more questions before you set sail.
Happy Cruising, Tracy V.