I was there last year (Punta Cana as well).
DR is a great place. People are friendly, food is good, nice things to see.....
I think Dec. though is their rainy season. The first time I went there, about 25 years ago on a family trip, we went over xmas and New Years, and it rained for 10 out of the 14 days.
HAve a drink by the pool for me!!!!
Have fun!