If the DR stop is at Casa de Campo, you will enjoy it! It's a large and beautiful resort, with golf, horseback riding, and a great little shopping village made to look like a Mediterranean town.
If not, it will probably stop in an area where there are other decent resorts, and you may be able to arrange some beach time at one of them. In any case, bear in mind that if this port were truly more unsafe than others
, Carnival would not stop there.