Its basically like that. For Big Thunder and Splash Mountain you don't get the rider swap ticket until the merge point with FP+, they give you a lanyard/badge (sort of like the one they use to estimate wait times, the card on the lanyard) and you give that to the CM at the merge point and they give you a Child Swap card there, to cut down on shenanigans I'd assume. We found the cards good for 3 people, they expired like a week later (so not the same day or hour), and you can go right into the FP+ line if you have a FP+ you don't have to wait standby on the first go-round. Also, they did ask to see the child every time, so bring them/stroller with you to the entrance to get the card. Also, the people swapping do NOT need FP+, we found this frees up FP+ slots for that parent to do 3 extra things geared towards the smallest child if they don't have a ticket/magic band (like M&G, etc) if the party doesn't mind separating for a bit.