Herbertoll,
Cabrera is a nice but fairly small and quiet town. There are several places worth visiting.
Restaurants:
Enzio's Italian Restaurant: right on the highway, south side, between the first and second light. Great seafood, steak etc...
El Dorado: on the corner of the first light coming from the east. Very similar to Enzio's but a little cheaper.
Dominican Resaurant: across from the gas station at the other light. Thatched roof place and a little hard to see. Good quality dominican food in an outdoor setting
Babanuco: Very unusual place filled with unusual artifacts picked up from the ocean. good food, but unusual setting. not for everyone. you will need a local to help you find it.
Catalina hotel: I have never been there but I hear it is excellent. Also very expensive. Get directions when you arrive.
Sight seeing:
We have a nice waterfall that might be worth a visit. some of the local kids will dive etc...
There are two fresh water lagoons that you might find interesting. good for a nice cool swim. Blue Lagoon and I forgot the name of the other one.
Lots of horseback riding availible but you will need to ask around when you arrive for more details.
There is plenty of great places to hike but nothing is organized around that. I would recommend hiking up past the waterfall and exploring the dirt roads back there. you will see lots of real rural dominican life, and some great views.
you could also go fishing. Check at the marina to rent a boat. The boat would be an open outboard type and it would be a rather simple affair. (line, hook, and bait, no rod). Or just find a good spot on the cliff. If you ask around someone would be sure to help.
I see a few tour trucks driving around every day and with 30 people you should consider asking to rent one or two for a good traveling party. I know they can be arranged through the catalina hotel, but I am sure your villa agent can arrange it as well.
Casa de Campo Golf course is just down the road. top notch course.
Rio San Juan (20 min drive) has scuba diving and a few dirtbikes to rent. I dont have further info in that. Also a nice lagoon and boat tours, good tourist type shopping (paintings, carvings, etc)
As for night life: Cabrera town square is always the place to be. Check out the disco (The Embassy) and the thatched roof bar across the street.
Beaches:
playa grande: (10 min west) really big beautiful, lots of sand, usually less crowded, fairly heavy surf. Volley ball court. Beach venders are availible for drinks etc but not aggressive.
Playa diamonte: (10 min east) small beach, hard sand, shallow water, no surf. mostly visited by just dominicans. Some people like it, some hate it. Great for small children
Playa Calaton: (20 min west, Rio San Juan) nice medium size beach. surf is mild but better waves farther out. some beach venders around but not aggressive. sometime crowded on the weekend. Best snorkeling (and spear fishing) here.
I am sure there is more but that is all I can think of now