1) You book your room as you normally would.
2) Add/ or book a second room as you would with number 1.
3) Apply GOH to rsvp #2.
4) It's pretty simple since you did say you are traveling with the,

or

you can always call MHC or Hyatt and done it how you done it before. "This used to be very easy: book multiple rooms, call Hyatt to apply GOHs and boom"