So, nothing gets attached to the Magic Bands.. That is the first thing you need to know. Everything is done in your My Disney Experience account. This is actually good news. This means that if your friends have their own
MDE account, they can set up charging on their MDE account. Then they will link their Magic Bands to their MDE account and everything should just work.
The key to My Disney Experience is that it is set up to handle families. In this case, both parents should have their own MDE accounts and list the other as family. Then all the children should be under one of the parents. It works best if the person who is most familiar with the system is the primary MDE account. For a couple with no children, it is very simple. They both have an MDE account and list the other as family. For a single person, all they need is an MDE account.
Generally speaking, if you have an MDE account you need to have told it about your upcoming stay (entered your confirmation number). Then, you need to load some sort of ticket media into your MDE account. All this needs to be done using the primary MDE account. Once that is complete, the system will tell you to customize your magic bands and they will be shipped to the address on the primary MDE account a week or so before their trip.
The reason I mention this is that your friends will have the opportunity to get their own magic bands which will be pre-linked to their MDE account. There is no 'room account' any longer -- everything is tied back to MDE accounts. If they do not have their own MDE account, they WILL NOT be able to set up charge accounts for themselves. Perhaps the CM at the checkin will automatically create an MDE account for them but I wouldn't count on that.
All in all, the new system worked well for us back in March, I'm sure they have some bugs worked out by now. Have a great trip!