Hi there!
Well, I've been to Cabarete a month ago and must tell you it's the paradise for kitesurfers and windsurfers. One of them told me he was renting a house U$1000 per week with some friends, so it would be cheaper. The only thing is that it wasn't in the town "center".
I stayed at Hotel Punta Goleta, and I think it's ok to go with infants, although you have to go through a bridge to get to the beach.
In my opinion, if you don't mind not going to Cabarete, though I love that place, you should better go to Punta Cana. I've been 4 years at the Barcelo Bavaro Palace with ALL my family (grandpas, aunts, uncles...) and it was so great. There were a few infants, 2 of them with just 2months and a half, and it was perfect for them too. I think you might need to change the place to have a better holiday.