Welcome aboard, Kathy!
I highly recommend that your teens check out
Disney Cruise Line's Teen Club,
Vibe! Once there, I have a feeling they are going to love it. Since they can go there together, even if they're shy, they'll never be without at least one other person they'll know to begin with. And it won't take long until they've met all sorts of new friends from around the world. My daughter still keeps in touch with an Australian friend she met there aboard our last cruise.
My children have loved every single moment of their time in
Disney Cruise Line's Youth Clubs, from when they were just old enough to enjoy Oceaneer Club and Lab, to the tween fun in Edge, and now my daughter, as a teen, at Vibe. Vibe is only for teens ages 14 - 17, so there will not be younger children there. It's a teens only space. The counselors there are hip and cool and know how to create activities that the teens will love and how to get them all engaged and mingling.
I definitely suggest that your teens attend the first night at Vibe, because quite often that is when there will be ice breaker type activities allowing the teens to get to know each other and the counselors. They'll also have some say in what activities will be planned for the rest of the sailing.
I think you'll all be surprised at how cool of a place this is, and how much time your two teens will want to spend there, as well as on the outings around the ship with the Vibe group. I only wish I had something like this when I vacationed with my family as a teen way back when!
Have fun planning, Kathy!
Marcy