Do both adults (or the full party) need to be in line to get the Rider Swap pass?
Or can my wife bring a little to the bathroom or lunch while I go through queue and get the Rider Swap without her?
Are the RS passes then FP+ locked, or can I go through twice with different kids (to accommodate said bathroom/meal needs)?
It is always good that they are close by when you ask for the rider swap. Sometimes they won’t give it to you unless the other rider is visible with child. Once you are past they can go and do something else while you ride.
What do they physically give you?
I only have experience with the Disneyland RS and over there they scan your Fastpass and a 1-2hrs return Fastpass gets added to your account. From what I’ve read it is not the same at WDW.
The CM at the ride entrance will give you a lanyard. Then the CM prior to loading will take the lanyard and give you a paper RS pass. Historically these have been good through the end of the calendar month and valid for up to 3 people. This seems to be changing as some on the ground recently have had their passes expire that day. It is not loaded onto your band like at DLR.