CJ there’re many more stories about people not being able to modify their reservations to increase guests than there are stories where it was no problem adding people.
And as many stories where someone was told if they wanted to add people, they needed to make a new reservation.
But, just like the NFL, on any given day, anything can happen, and probably will.
In the near future, I’ll relate a story about upgrading 5 day park hoppers to Florida resident APs after all 5 days have been used up.
We all know the rules, so I won’t go back over them, only to say that it pays to take the time to get the right CM on the phone to work out the problem before you return to WDW.