As far as linking..... they create an account.... and then how? Do they friend me? How is it done? I can see my Dsis on there from last time,I'd like to get setup well before any booking windows. Not too concerned about people being onboard,really mostly for a few things together etc. as far as DP goes, what's my best plan for getting them in same window? All at once or one a acct at a time?
For making ADRs, when your window opens you would make an ADR for 14, then it will take you to a screen where you can add each member to the ADR list from your existing "friends and family" list. So, you would need to have everyone set up with their MDEs, either before making the ADR or down the road. You can add them at a later time too. You're not changing the reservation, you're "assigning" a person to one of the 14 spots you already have.
It's not a big deal if you make the reservation and not add each person, they just won't be able to see the ADR in their individual MDE.
One thing to keep in mind is that sometimes larger parties need to call Disney to make ADRs. Sometimes you can't do it on MDE.
FP+ are a different story because each one is linked to an individual magic band. If you are making all the FP plans you will have to choose people from your friends and family list in the process of getting FP. You will have better luck if you split that large group into overlapping time slots.
It's been a while since I've done it, but if I remember correctly after a person creates an MDE account, you can search for their name in your MDE and they send that person a request or invitation to be a part of your friends and family list. I also think that members have the option of who manages their plans, so if you are making plans for all the others, they have to give you permission in their individual MDE.
There is an option in MDE to "share your list" which makes it easier for groups to connect with each other.
We travel to Disney with extended family about every other trip (every other year, usually). It can be fun, but also draining. It's good to set limits and not try to do everything together.