We just returned from our 8 day Disney trip and we did FOP a couple of times during the week. We had 5 children aged 6 and under in our group, and only 2 of them were tall enough to ride, so we had to utilize Rider Swap a lot. In total, ours was a group of 10 - 5 adults (who ALL wanted to ride), and 5 children (only 2 could ride). We all had FastPass but did not all have to scan them in order to use Rider Swap. I would go up with my husband & two children and go to the FastPass line. I would gesture to my kids in the stroller and say we’d like to use the Rider Swap. I would then be given the lanyard, and then my group would walk together over to a space where we would have the kids wait. Then I’d take my older daughter in line with me while my husband waited with our son, and when finished, I’d give him the paper pass so he could go through the FastPass line, letting our daughter ride twice. I think this would be the same with the Standby line - your kids won’t have to wait in line unless someone is really misinformed.