I've volunteered at the Adventure Aquarium for several years, but I'm on a bit of a hiatus right now. To become a volunteer you need to do a pool test, get a dive physical (and every year after), CPR cert., and drug test. Obviously you also need to be OW cert.
The routine is a mix of maintenance (e.g., scrubbing algae off rocks, vacuuming the bottom of the tank) and dive shows. The dive shows are fun because you get to wear a full-face mask with a microphone so you can talk to the kids outside of the tank.
People either really love it or get bored after awhile. If you are going to feel put out being asked to do a lot of maintenance, I wouldn't sign up. On the other hand, it is pretty cool cleaning rocks with a hammerhead shark swimming by! There's nothing quite like diving in tanks with that much sea life.
DM me if you have more questions. I can put you in touch with one of the dive safety officers if you you'd like.
Best,