OP...
I guess I would ask you to look at it this way (and this is only my world view, I am not juding anyone)...If you were me you would have three children. No way I can wait in one line and DH can wait in another line and then we can get three kids in without causing trouble. Is it fair to my children that they have to hold their own places in line but only children are "more speical" and don't have to ever do that...they can just flit back and forth to the front of each line that someone else stood in? My whole point, how do other children feel? I know my boys would hate it if they saw any child seeing twice the characters as them in the same area with the child swap thing. It's not that you probably cannot get away with doing something, but it might cause others to feel uncomfortable or upset. And no, I don't think every child is counting how many characters another child is seeing...but if they were to notice it would feel hurtful (fairness is a big thing for kids, they hate to feel as if something is not fair, at least my kids).I guess I figure other adults can handle little things like that but I don't think it's worth making another child's day any less magical.
Before anyone gets upset, NO the world does not revolve only around my children...but I do expect that when they pay the same price as an "only child" they should get the same service...if they have to wait in line, so should every other child. The exception to this rule is for those who have "real" speical needs and then they should procure a pass. When we travel with a family with an autistic child they always get a pass for him, he then takes his pass to a line (attraction or character) and is usually given a "fast pass" type pass for him to come back when they estimate he would have gotten to the front of the line had he stood in it).
If Disney thinks kids waiting in line is not something they want to happen then they better do a total revamp (not sure how on EARTH they could/would be able to do that) and offer it to every child. Until then my personal feeling is that NO child is more deserving than any other of a place at the front of the line. I KNOW THE OP DID NOT MEAN SHE THOUGHT THE CHILD SHE WAS WITH DID...I am just stating my opinion as to all kids.
OP thanks for asking about how others feel. It shows that you do care!!

And even though this is how I feel, I still say follow your heart/the rules in all matters and you won't be led astray...even if they are counter to what I think!

Above all, have fun, you'll be at Disney and life is too short to waste one minute of it...especially a Disney minute!