[ashesmod]

Go on MDE

Click on Myplans
(This will show all your fastpasses)
Click on a booked fast pass you would sacrifice
Then Modify
Then click the members you want to modify
Then you can search what's available
(Remeber to change times etc as this will show further availability)

You original Fastpass will only be cancelled when you confirm a new Fastpass. If you don't you will not lose your original Fastpass