This is a difficult age to be on a cruise in my experience. I've cruised with both my kids in this age range, and your concerns are legit. As fireclan mentioned there may be a specific meet and greet for your age range, and if not, I believe you can request one. But it is hard... Too old for the teen club, too young for the bars. As Moby Dick mentioned it's probable you can get into the bars, but speaking for my own kids, they just weren't comfortable socializing with people that much older. For the cruises where this was an issue for our family, they ended up hanging out more with us, it's just the way it went. If that's not an option, definitely see about the meet and greets for your age range.
Okay I just saw you're on the Odyssey... So in the Mediterranean I believe the rules are you can drink in the bars, but double check that. If that's the case, that's probably where your age range will go.