I don't see why this should be a problem. There's no reason they would need to be on the reservation - mom and dad could be staying offsite or you could be meeting local friends or a variety of reasons. What I don't know if is you can pick up 8 tickets with only 4 people there but I don't see why not as long as you aren't using Florida or military rates or something where ID would be required.
If you still have the cards that you used and they're from the same account, you could also use those like you would a MB (or in addition to them). If you're using a different account, those old cards could be used for SDFP as well.
The tickets are under one will-call order in my name that was comp. from Guest Services from a bad experience from a MNSSHP last year.
I'd probably opt for phantoms instead of a second MDE. You'd have to log in and out of two different accounts when making and/or modifying the FPs. Just seems like an extra unnecessary step. Unless you had two different people/phones accessing the accounts.
Some answers (I don't know all):
1. Yes, link it later and then enter the MB number (on the back) to assign it to each Rogue.
3. There's no reason for them to care about your rogues. I have approximately 25 people in my MDE and none of them are rogues, just people who have visited the park at some point - my sons' girlfriends, grandparents, nieces & nephews, friends, etc. Some had their own MDE and others I just managed and made all their FPP's for (and bought their tickets, etc.). Not having everyone you're linked with on the same trip is not at all unusual. I would be more concerned about the "cheery and helpful" CM at the kiosk trying to help you but a polite "Thanks, but I'm good here" should be all you need to say.
4. I would probably not wear both on the same arm, just for comfort reasons and because it would make it a bit harder to scan the right one. I'd wear normal ones and either have the spares on a belt loop, around my bag, or on the other hand. Or have a person with a backpack keep them all in one pocket and just hand them out for each "rogue" ride. Remember that they'll all need to be scanned at a kiosk at the beginning of the day so it may just be easier to have one person keep a hold of them all. However, if you decide to wear two, no one will notice or care.
5. Just be sure whenever you stop to have pics taken that the band you give the PP photographer is one of the "legit" ones. If they're all tied to the same MDE account anyway, it really shouldn't make a difference though. As long as you have a band (any band) on the rides that don't have a place to scan (7D, FEA), it should automatically read and add those pics to the MDE.
Unless I'm really missing something, you can never book more days of FP's than you have tickets for. So if your parents' tickets have one day left, you can book one day. However, once you use that day's FPP's, you can then book for the next day and so on. Other than for the biggies at Epcot (FEA, Soarin') and 7 Dwarves at MK, usually there's pretty good availability even booking the day before and it saves you from having to go to a kiosk that morning like you would with SDFP (plus you can make changes from your phone assuming you have their login or are linked to them).
If you're using the same set of MB's or cards, you will be limited to one at a time at the new park.
In general, my experience is that they like to have everyone scan their own in a 1-to-1 correlation, unless it's obviously for a small child or someone who might have difficulty scanning their own for other reasons (when we took my almost-90-year-old inlaws, I just carried and scanned theirs). It would be less a concern that they had different MB's and more just difficult for them to keep track of who had scanned and who hadn't. Most likely, they wouldn't stop you or anything but it might clog up the FPP line a bit for others so I'd say the easiest thing would just be to hand everyone one as you approach the line and collect them either after scanning at the first (or second, for the few rides that still have it) check point.
