Not sure what you mean about fitting the parent swap in a window. The only thing you have to manage when using the swap is the group going in using the FP. You still get a paper pass for the swap which can be used any time that day (and usually for at least some number of days after) so both sets of riders do not have to ride during the FP hour.
Suggestion for FP with a party of 5 riders (not counting 1 year old and assuming you're going with spouse) - for each FP slot for big kid ride, have two people make FP for one ride and 3 people make FP for a different ride (or if it's a ride you want to ride more than once - the same ride at a different time slot). At first ride, the three with FP go first. With the rider swap the two waiters go (and get to bring a third with them). For second ride, the two with FP go first, and the three waiters use the swap pass. You can get six FP rides that way (although you're split up a little bit more).
