Ahoy, Jon!
Thanks for stopping by the Moms Panel with your question!
One perk of sailing with Disney Cruise Line that we've truly enjoyed is access to the amazing
Youth Clubs. Each club is staffed with highly trained Youth Counselors that are great with kids. Our girls have spent time in every youth area - from the nursery to the teen club, and loved every minute! It's awesome for kids to have a safe, fun place to go where they can interact with other cruisers in their age group. It also gives the adults time to explore the ship on their own, and visit the adult-exclusive restaurants and clubs. No reservations are needed for ages 3 and up - they can visit the clubs anytime the doors are open. It's included in the price of your cruise!
In your situation, I'd encourage you to have the kids visit the clubs for their specific age groups on your first afternoon onboard. The 17-year-old would be assigned to Vibe, the teen-exclusive club (ages 14-17), and the 13-year-old to Edge, for tweens (ages 11-14). They might find that they prefer going to two separate spaces to hang out with kids in their age group! The activities in each space will be tailored to the ages of the kids, so I'd make sure your younger guest checks out all that will be happening in both spaces.
If they decide they prefer going to the same youth club, you can speak with the Youth Counselors about having the youngest one "age up" to Vibe. I can't guarantee they can make an exception, but they always seem to go above and beyond to make sure each guest has the best experience possible! My daughter chose to do this on one of our cruises, and we simply had to sign a form saying we gave our permission for her to be a part of Vibe instead of Edge. It worked out great, and she had a BLAST.
I hope this helps!
Have a magical day! - Diane W.