If anything, you can get familiar with the unloading areas, or the areas right outside the loading areas instead of not necessarily waiting in the child swap area. As those seem pretty cut and dry.
This is typically did with my father since we'd do SR lines (so sometimes we'd be in the same ride vehicle, sometimes we would not). As AP it was easy to find out what the typical unloading process was, as well as the exiting portion, so you'd probably have to watch videos on what it looks like. However, what we typically did was once we got off, we either stood in the unloading area, as off to the side as possible to not block people from leaving, or if TMs seemed to want that area clear we'd just start moving towards the exit and during the exit part (which typically was a hallway) we'd just off to the side to wait.
Typically it was fine to just stand in the unloading area off to the side (especially since it's only one of us). I only mention you might need an alternative, because I would imagine there might be a TM someday that might want you to move along, or get out of the way. However, I doubt it, as you're waiting for your children (they'll know that) and it's easy to stand and not be in anyone's way.
Also a good reason to have an alternative is, because for example, some immediate unloading areas you wouldn't be able to meet them at. The Mummy (for one ride) technically two unloading areas, as there's two coasters. So, typically, we'd meet at the area in which there is a doorway that leads down the ramp off the ride (as one rider is able to walk right to that door way immediately and another would have to walk over stairs in order to get to the doorway).
I mention this as being an option, because if you prefer to see your children as soon as they get off this might be the best method, because once your children get off the ride, they'll need to have a TM to escort them to the child swap area, as some of them are right when you get off and some are not. However, the child swap option is good too, because regardless of where your children end up, they can ask a TM to escort them to you.
Also, to answer your question about Gringotts I do not know where the child swap is, as I never personally noticed it in the many times that I've exited the ride. So, it's either not in the path of the exit, or it is during the exiting process, but they do not make it obvious. When I googled images of it, where the sign is, is also where I see wheelchair signs for in the background, so it's more than likely off to the side in another hallway that most of the exiting guests do not enter.