To add to the above info, I'd suggest you set up all of the profiles in MDE *first* before anything is linked.
I highly suggest that every adult on the trip go into My Disney Experience and create their own account. If there are children, one parent should add them as "managed by them" profiles. Then everyone else can link to each other. The easiest way to do that is to have *you* become friends with everyone, and then everyone friend-request everyone else using the "people you may know" feature. If you can all sit down at the same time as a group and do it, it shouldn't take you more than 15 minutes. (Otherwise it'll drag out as some people do things immediately, others have to keep getting reminded)
Having this solid base of profiles set up beforehand will help make the later steps of linking hotel and tickets, and then eventually FP+, much, much easier with such a large group.
-Rob