I don't have kids, but I have done Salsa and Salsa in Cozumel and Cabo. Both experiences were similar. First, it's a lot of sitting. The salsa dance lessons don't come until the end. Any beach time was sort of on one's own after the salsa-making and the salsa dancing.
At Cozumel, you start with a lesson in margaritas and make a traditional one first, then learn how to make a strawberry one (that one gets poured for you). They have nonalcoholic options for those who are too young (or opt not) to drink. At both times I did this excursion, we were in port with other ships and so this excursion was filled with other cruise passengers at the tables. Unlimited margaritas are offered, so you can expect to see things get silly pretty quickly. At Cozumel, I think we made 6 different salsas (it's mostly cutting vegetables, mashing things with the mortar and pestle, or combining ingredients). I don't see Costa Maya on the official website (but do see it on
DCL's) so I suspect it's a "travelling version" that's abbreviated.
The website is
http://www.salsaandsalsa.com
You get unlimited tortilla chips for your salsas, a cheese quesadilla, and some chicken taquitos.