Maybe if you could clarify a few things for us, we can give you more accurate answers.
1. Who s "everybody"? How many people we talking about here?
2. Some basic info about Mac model, HD capacity and fullness, RAM etc is always helpful.
3. If you're an admin, why don't you simply change the other people's accounts to "user"?
Oh wait, I'll bet what you're saying is that you have multiple people using the SAME account. Ah. Yeah, that is (IMO) a bad idea.
If it were me I would have each user buy a thumb drive of the desired capacity and copy over everything they need onto it. You can share a common music library but I recommend NOT sharing a common photo library.
Anyway, once they've copied the files they want to keep onto their own thumb drives, you set up the user accounts for each person and they can log into those accounts and add the stuff from their thumb drives into their accounts. Once that's done you can remove everything they took out of your account.
Needless to say, it would be better still if "everyone" each had their own Mac or iOS device for themselves.