Anna,
Hello from Indiana!
When it comes to
Rider Switch, Disney asks that the child not riding always be attended to, and not left alone or with just another child. Your 16-year-old would certainly qualify to watch that child while you and the other teenager take a spin on the attraction.
While they do list Rider Switch-eligible rides on the website, it is always important to check at the attraction itself, as these programs can change from time to time.
BONUS TIPAs my girls have both become teenagers recently, we have started to enjoy not just our time together as a family, but also the fun of splitting up into smaller groups for a part of the day. Splitting into two or more groups can allow everyone to be more focused on the attractions, shows, and experiences that most closely match their interests. What we do is spend the first part of the day together, then break off just before lunch. We later reunite in the late afternoon for one more all-family experience and then we are off to dinner to recount our day's adventures.
On a recent trip one daughter and I did some afternoon resort hopping to take in the different theming and view the animals at
Disney's Animal Kingdom Lodge. The other daughter headed off with Mom for her first ever spa experience. At dinner we had so many fun stories to tell, and everyone agreed it was one of our best Disney days ever!
Have a Magical Vacation!
Doug