Does mom and dad need to use a FPP for Character meets if DS4 uses one?
Yes.
Would this scenario work?
Dad books FPP for Space Mountain
Mom and DS4 books FPP for character meet.
Family shows up for Space Mountain and do Rider swap and Dad rides followed by Mom
Mom and DS4 do character met.
This will be our first trip to WDW How do the character meets work? Would I be able to witness DS4’s interaction with the characters?
Anyone who wants to meet or view meet must have FPP. They are indoor and you would not be able to view without. You could do what you planned but dad would not be in character meet.
If you are staying on site, meet princesses in morning EMH. Also I was able to get day of FP for Rapunzel and Tianna at MK later in the evening. You could also do a character meal with princesses so you could all meet princesses at the same time.
Anyone getting in the FPP line but have a FPP, doesn’t matter if it’s for a ride, show, or character meet.