Yes, the same child can go both times...first w/ one parent, then with the other.
So, get your FP's for everyone in the group that will ride...then go back later to ride--enter the FP line...the CM there has to see EVERYONE in the party that is going to be riding the ride using the child swap option...then they will give one parent a special colored child swap ticket type thing...it says the name of the ride on it and to bring it back w/ the kid.
So...then the kid and one parent (not the one that is holding the special colored child swap ticket) go on the ride.
The other parent can go do some other ride w/ the little one(s) that can't ride the "big" ride....
When the 1st parent and kid get off, meet somewhere...then the 2nd parent takes the big kid and usually goes to the exit (for SM, for sure I know this is how it works...but not for soarin'...just my 2 experiences)....and then you get to jump right on w/ the kid the 2nd time...
the colored child swap ticket is all you and the kid need...that's enough for both of you....and it's basically treated like a FP...you don't have to stand RIGHT there waiting for the 1st parent to get off w/ the kid....you can just go back w/ the colored ticket at a later time (like a FP) and hop on...they have no clue how long ago the 1st parent rode...
Just my experience last week--it was great! I was the 2nd parent and we walked RIGHT ON to SM and got perfect FRONT ROW seats w/o a second of waiting!
(The hardest part was finding the freaking EXIT...which is how the 2nd parent and kid have to enter after the swap...I had to ask 2 or 3 CM's to find it!!)
HTH!
