We were there last February with my 15 yr old DD and her friend. We did not eat at Margaritaville, but did eat on the outside patio at Hard Rock and watched the sights on Duval St (!). They enjoyed that restaurant. The sunset celebration, as mentioned by others, would be a "don't miss". Our teens (and US) also really enjoyed a bike trip (our B&B rented us bikes) over to the beach at (I think) Fort Zacahary Taylor Park. Interestingly enough, the girls both enjoyed Ernest Hemenway's House/Museum...it was literally around the corner from our B&B so we "dragged" them there. They both had had to read The Old Man and the Sea in their sophomore English class a little earlier in the school year. They really "got into" both the organzed tour, asking questionsetc., and then wandering around the grounds taking pictures of each other and the six-toed cats!
One thing they did NOT like was the abundance of (protected) wild roosters all OVER the place.......the ones outside our B&B crowed at streetlights and stuff ALL NIGHT LONG! LOL