Ocean Blue/Sand is very lovely, has beautiful pools, very good food with very wide selection, several thematic restaurants that do not require reservation (American, Mexican, Italian, Dominican, Gourmet, Seafood) and a lovely cofee shop a-la Starbucks, where they serve cofee, tea, frozen delights, and pastry. You can read the international newspapers in a plushy chair while enjoying your frapuccino and smelling the roasted cofee, with a nice non-intrusive music in the bacground. Also taste one of the best cheescakes I have eaten in the DR.
If they check in into VIP service (Club Elite) they will also enjoy room service 24 hours, free horseback riding, and premium drinks.
Everything is within walking distance, the hotel is not large but not small either (800 rooms) and it's 5 minutes walking time from the beach to the reception. The hotel also has a bowling alley and climbing wall. Got late-nighters, a sports bar is open 24 hours and serves late night hot food.
Another hotel I can recommend is Melia Caribe Tropical. it has lush tropical gardens, and it really is paradise. It also has several thematic restaurants, including japanase one where they cook in front of you. It also has really nice pool and food is plenty and good. The disadvanatge is that walking rakes up to 15 minutes to get from the reception to the beach, as the hotel is really huge.
At Melia CT, they can also enjoy a private Royal Service section, with private pool, 24 hour room service, provate restaurant, and premium international drinks.
Other hotels I can recommend in the area are:
Bahia Principe
Palladium Punta Cana (of the 3 palladiums this one is very recently renovated)