Think outside the box as well. No reason to limit yourself to a standard hotel.
If there is a group of you, you might want to look into renting a private villa in one of the gated communities in Sosua / Cabarete. Or look at renting a condo on the beach -- lots of beautiful properties on offer there as well.
I know that the Ocean Point project does short term rentals, as does Ocean Dream -- both of these projects have beautiful condos. Sea Horse Ranch has some amazing villas. Sure, they're expensive, but if you have a couple of families sharing a villa, the price per head becomes competitive. There are many more options available to you, but it will take some digging.