Man, my kids love the place. They can't wait to get back for their third time (in March). And we're trying to be sure we don't do too much, as we have in the past. All of us are trying to make it a point to NOT book a lot of day trips or plan all that much. A good book on the beach or dip in the pool keep my younger ones (pre-teens) completely entertained. The teenager likes just walking on the beach or hanging out with the rest of us as well. All of them think the infamous chicken drop (which can be completely free) is a riot. A day's cart ride north with lunch somewhere can, by itself, be genuinely memorable.
Heck, we've been accused of BEING the show at some places we've been.
How much entertainment do you need? Perhaps you're better served by being in a more "touristy" environment...maybe Cancun or Playa Del Carmen? No lack for diversions in places like that, but be prepared to pay for them.
Honestly, one of the best parts about San Pedro (for me) was the affordability of the place. I seriously consider the bang for your buck there to be one of the best vacation values you'll find anywhere.
But don't tell anyone. Too many people already know about it.
Sorry you had a less than pleasant trip. But live and learn. It's a big world with lots of possible destinations for your next trip, eh?