Or for a bit more fun there is a water park in Casa Linda, Sosua. Very reasonable entry fee and a poolside bar and restaurant. There is also a water park at Sosua Ocean Village. A bit more expensive, but still a nice day out for the little'uns.
Don’t go to Casa Linda without phoning first. It’s been closed for renovations for a long time. It was $150 pesos for entry in November m, but they were closed then with no date of reopening.
SOV Laguna has an area for smaller kids and water slides for bigger kids. The first one on the right hand side was also closed for renovations as recent as December, and I doubt they’re open yet.
The SOV Safari Park at the end of the road, past the Jay-Z/Roc-a-fella hand symbol sculpture was open in December. It also has a shallow area for kids plus some water slides and several pools.
A Day Pass is $1500RD Consumable/which means with food for adult and $500 for kids. We ate lunch and dinner there and still took food home.
SOV Safari Park Day Pass
SOV Santa Fe is a little less suited for younger kids but still has a shallow pool. A Day pass /Consumable there is $2500RD for adults and $1500 for kids. We didn’t eat near that amount of food at lunch, and took a Large Pizza & 3 smoothies home to boot.
I don’t know if that’s out of your price range? I also know of an apartahotel in Sosua (relatively free of putas) that will allow a day pass for $350RD for adults and kids are free. I have to look up the name and find it on Google maps.
There is also a country club toward Sosua up in the hills, but I don’t know what their costs are. I’ll Google and see if I can find it for you.