So the new MBs are from your secondary-account resort reservation. So they're already linked. The bands are already phantoms, right now.
The
MNSSHP tickets are a separate issue. You have some choices.
1. Don't link the party tickets. They don't have to be linked. Just use them at the kiosks for SDFP. You can also use the 4 bands for SDFP. That means you'll have a total of 8 sets of SDFP any time you visit a park.
2. Set up four new phantoms - probably do it on your primary MDE to keep things simpler in the future. Link the MNSSHP tickets to these 4 phantoms. You'll still have 8 sets of SDFP - but you'll be able to view the choices you made (at the kiosk) from your MDE online for the party phantoms.
3. You could link the tickets/cards for MNSSHP to the resort-room profiles on the secondary MDE. The MNSSHP cards will then become clones of the bands. This can be convenient - as they're easier to carry around than the bands. But then you would only have 4 sets of SDFP (since what's on the cards will also be on the bands and vice versa).
Presumably you booked your resort stay via your son's Hub account to get the cast discount?
Does he have any unused comp tickets on the Hub? If so, you could link them to one of the MNSSHP ticket phantoms and prebook a couple of sets of FP (GLFP).