Cool. So I could make choices/changes using my iPhone that would apply to my parents' bands as well, provided I set them up as friends/family under my Disney app...is that right?
You have two options when handling others in your group:
1) Have them create profiles of their own on the My Disney Experience site and everyone friend-requests everyone else so that anyone can make FP+ reservations for anyone else. This is the required option for anyone who wants to log in (online or via mobile app) to change their own FP+ reservations
2) The "leader" of the group can create "managed by them" profiles under their own MDE login. They would then be in charge of FP+ reservations, Magic Bands, etc for those sub-profiles. This option is usually the best option for young children who wouldn't want or need to log in on their own. People who have their own profiles under option 1 above can still "Friend" these people with the option 2 profiles after they're created, giving them access to making FP+, etc. on their behalf.
While Option 2 *might* sound good for your parents, if they're the "owners" of the resort reservation it might get a bit complicated. In that instance, having them create their own profiles, linking them and then never dealing with them again might be their best choice. Since they've been DVC owners for so long they most likely already have a login account on the Disney site. They should go in through that login to create their profiles under MDE. One of the biggest problems that I read about cropping up are when people have multiple log-ins on the Disney site (one with just a username, one with their email address as the username, one with an *old* email address as their username, etc) and various reservations get made under different accounts...
Also, even when you create profiles under Option 2, the people associated with them can still eventually "take over" control of the profile in the future simply by the owner of the main account selecting the "Invite" button and sending them a friend request. Once accepted, the other person will then "inherit" the profile and control it themselves. This is helpful when you have a situation like a child who originally didn't need to access their profile, but then gets older to the point where they want to log in themselves.
I think the main thing to keep in mind to minimize the chance of problems cropping up with profiles and linked accounts, etc is for everyone to create and inter-link their accounts *before* you get started planning and linking your vacation plans.
-Rob