In Cozumel there was a store with small wooden puzzles made in Mexico for $1, and on Grand Cayman there was a store where I bought pencils for $1. They were colorfully painted, with wooden fish, parrots, etc. on top and said "Grand Cayman Island" on the side. I don't remember the names of the stores though, sorry. I would think most "souvenir" stores would have inexpensive items you could get for the kids though.