I have heard the night life in Punta Cana is mostly at the resorts. I've read the closest "disco" is about a 30 minute taxi ride from the resort.
I have been unable to find any positive diving reports for the Punta Cana area. Looks like most of the better diving is on the North Coast. But I have been in touch with some of the dive operators and they have said from the Allegro resort there are 14 dive spots available, Ranging from 45 to 60 feet. Visibility has been quoted as 60 to 120 feet depending on the weather. I've heard the reefs are in pretty bad shape. The prices I've found are about $50 (US) including equipment for 1 dive, $80 for 2 dives, and $180 for 5 dives. They do 3 trips per day, 2 in the morning and 1 in the afternoon. One dive per trip (duration trip 90 minutes, bottom time 45 minutes)
This will be our first trip to the Dominican Republic so all my information has come from research I have done on the internet. (I hope I haven't told you anything wrong)
As far as Holy week - I was in the carribbean last year at Christmas and a lot of the shops were closed for Christmas Day. I don't know if Easter will be the same way. We are going Feb 18-25 so if you want I can let you know how our experience was when we return. Check out debbiesdominican.com, they have some great reviews of the Allegro Bavaro. I have found a lot of information on that site. You might also check out
www.scubadiving.com they have dive info on all the islands. Good luck.