Punta is great for teens and pre-teens. There's a lot to see and do. Five days is not a lot though. I suggest staying in La Barra and not at the Conrad which in my view though in town opposite the beach is not in the best location. Better is the La Mantra which is one of the better hotels in the area. You'll need a rental car if you really want to enjoy the place. Punta is good for sports, there are many different types and styles (e.g. for teens, for families, for the cool people, etc) of beaches.

FWIW - Argentine and Uruguayan teens (even most of the 14 year olds) tend to go out in Punta till 5 AM - your kids may be envious. Also - nothing really gets going till 10PM (Dinner included) so you'll have to adjust your schedules.

If your teens kids speak any Spanish this would be very helpful - as Punta is not geared towards English speakers.