In Puerto Vallarta, the Malecon is a beach promenade right in the downtown. It's not the best beach for snorkeling or swimming, but they have parasailing and jet skiing from this beach, and lots of activity. It's right in the middle of the pretty old-town area of Puerto Vallarta too -- with, cobblestones, shops and restaurants. It's easy to get to by shuttle or taxi from the cruise pier.
Yelapa is a farther away beach, only accessible by water taxi. It's got an "island" type feel, with palapa restaurant, palm trees etc. There are watersports available from the beach, but it's got a quieter, away-from-it-all feel.
There's also a jungle canopy tour in PV. We didn't take it, but might be fun for teens.