You don't unlink the reservation since the reservation number remains the same. In
MDE some changes may occur automatically, such as the planning party section dropping the ones no longer on the reservation. What you will need to do is add the new guests to your family and friends, if not already in that list. Then it is simply an issue of doing what is needed to change whatever is already done -- e.g., add or transfer park tickets for them, modify park reservations, etc., changes that can be made in MDE.