When people talk about late nights and party behavior they are normally talking about Cabo San Lucas. We never stay there. We stay in San Jose del Cabo. We are in most night by 8pm, except on Thursday Nights. On Thursday Nights San Jose del Cabo has an Art Walk where the Galleries stay open late and have Artists present. There is a Gran Mayan in San Jose del Cabo. Actually we like Cabo Azul better. The Airport is actually nearer to San Jose del Cabo. Though I do admit that most of of the Fishing and Snorkel Boats are out of Cabo San Lucas. There is Golf in San Jose del Cabo. Most activities - Fishing Trips, Snorkel Trips, Sunset Cruises - will provide round trip transportation from your Resort. As for flights I doubt you can direct flights to either location ffrom the East Coast.
As for snorkeling in Cabo there are two ways to do it. Pay for a Snorkel Boat Tour (includes food and drink) and they take you either to Playa Santa Maria or Playa Chileno. Then you get to enjoy snorkeling with a hundred other tourists, many whom have never snorkeled and have been drinking. Rent a car and drive to Playa Santa Maria or Playa Chileno. Arrive about 8am no crowds, wind, or waves. Have a great time and when the snorkel boats pull in a couple hours later go sit under your palapa and pull a nice cold water and sandwich out of your cooler. Wait for the hoats to leave and then go back in or head back to the resort.
Another great snorkel activity is to snorkel with the Whale Sharks in La Paz.Hard to do from Neuvo Vallarta. This is best from November to February. Again they will provide round trip transportation. There will be breakfast at Hotel California in Todos Santos (total waste of time) or a lunch in La Paz (better deal). Todos Santos is not worth visiting. Most people do not realize there is no tie between the Eagles/song Hotel California and Todos Santos/hotel Hotel California.
Oh we are in our 60's and we do this stuff. We also zipline, etc.