I am sorry, but no, you shouldn't be let back in line. Prepare yourself and your child for the upcoming wait, including MAKING them go to the bathroom, not just asking if they have to go and hoping they say no.
People that expect everyone to cater to them have a sense of entitlement, plain and simple. No excuses one way or the other. It would be nice to be able to take kids out of the line to occupy them, but it isn't feasible in most rides. If your kids can't wait 45 minutes in a line, don't take them on the ride. Wait until they can. Think about it from the shoes of all the kids who are being good and waiting their turn, when they see kids just strolling up and joining in. It isn't fair to the kids who can behave and patiently waited their turn.
Exactly. We had this happen to us at Sesame Place. My DS, who was 2, waited with us for the Big Rubber Ducky Raft Ride, for an HOUR, and then a Mom and her 2 kids ran through the line and joined her hubby. These kids were like 5 and 7! They had been on 2 other rides, and Mom told Dad all about it while we waited. I was HOT!!!! I mean hot. I reported them, but all I got was lip from the Mom who cut her kids into line.
I understand a bathroom run, to a point, but to have your kids on other rides while my son stands and waits his turn, and then see your kids cut in the line, well, that's not fair, IMHO. From the time he was very young, I have always explained lines and waiting to my DS, who is now five. We make a game of it now. We count how many people are in front ofus, and try to count how many more turns we will have to wait, what color car/Dumbo/carpet will we get, stuff like that. We have had people "save" spots, in WDW and elsewhere,and I have to explain over and over that we don't do that, we wait our turn. It is very difficult to explain why we follow the rules and other people don't.
And Disney does offer special assistance to children with Autism and ADHD, with a doctor's prescription. A good friend's son is autistic, and they are going in November. It is sort of a specialized Fast Pass that has a limited number of uses, from what my friend is telling me.