Sorry, to say but the mom's panel is often wrong. In this case, there are definitely wrong parts to answer as the description of how the rider switch card is used is off. They do not send people through the single rider line (first, only three rides even have one) - the rider switch card is good for more than one person and these people get to ride together, not something that can happen if they use the single rider line. They also do not make the second rider wait in specific area - the "second adult" is the one with the too short child, does it make any sense to make the small child wait? No. The second adult and the child can go on another ride, get a snack, or play in a nearby playground.
Since that part of the answer it wrong, I wouldn't trust any of the answer.
I agree that the Mom's panel is often wrong. There is a disclaimer on the bottom of each page that sys they do not speak for Disney and there is no guarantee that the answer is correct ( kind of paraphrased, but that is the gist of it).
In general, Rider Swap is used for attractions that have height requirements, not ones where some kids might be afraid or people might not want to ride.
One of the maon reasons for the Rider Swap with too short kids is that they don't want to let too small children into the line - there is too much chance of someone trying to get a too short child in and actually ride with them.
People whose children are tall enough to ride have options that people with sma
Ers children don't, including going thru the line and using the chicken exit.
So, I think the discussions about changes in Rider Swap are basically going back to the way it once was.
Also, the Guest Assistance Card is for attractions the person with a disability WANTS/WILL be riding to give them the accommodation they need to be ble to ride it. It's not supposed to be used when the person is not going to be doing, so be prepared to be asked which member of your party is the one with a disability and to be told they must be with you on the attraction to use it.
So, my suggestion would be the same as the other posters - get Fastpasses for each member of your party, including the child who won't be riding. That way, who ever sits out with the child can ride with another person. Or split up and decide no will ride what.
We do both of those and there is no question or problem with them.
While you may be able to get a CM to do what the Mom's Panel person posted, there is no guarantee and no guarantee it will happen even at the same attraction later in the day.