: . . . I want something they can start learning to roll in, and paddle on
: into early adult.
: After hours on the Yost site, I'm leaning toward Sea Otter-R.
: Am I on the right track? Any thoughts?

NO on the Sea Otter.
Your best bet is the Sea Pup - "Paddler weights range from 75 to 140 lbs".
The Sea Rider or Sea Rover or Roldarka are also good for rolling and enjoyable paddling for larger kids.
Most kids/teens will be flopping around in a Sea Tour. The are not ideal for learning to roll and have far more volume than needed for what you describe. Same with a Sea Bee.

Good luck!
Dave