Hi Penelope!
Thanks for coming back to the Disney Parks Moms Panel with another question!
The Rider Switch Option is actually the reverse of what you described. This option is available for adults who would like to ride select attractions at Walt Disney World Resort, however have a child that is too young or does not meet the height requirements for the attraction. When you enter the queue, inform the Cast Member that you would like to use the Rider Switch Option and then one adult will experience the attraction, while the other waits with the child. Once one adult has finished the attraction, the other adult in the party will get to experience the attraction without having to wait in line twice.
Many attractions at Walt Disney World will accommodate three people in the seats, my husband and I fit comfortably with our daughter on many attractions. If there is not enough room, I would recommend simply to have one adult ride with the child in your party, while the other rides in the seat behind!
I hope that helps to clear up the Rider Switch Option Penelope. If you have any other questions, please come back to the Disney Parks Moms Panel. We love to help!
Stephanie