I would stay put, and (I would totally do this given my mother and her personality 'quirks'), I'd say I would lose money on a deposit or something to do with my TA if I moved. My mom loves to control her adult kids, but she loves saving money more and would totally be for me 'saving' money. Beside the fact that I wouldn't want to move from a resort I worked hard to get, to much family togetherness makes for stressful trips (been there, done that).
Also, you might suggest that your dad and step mom get a RR at POR. At your sisters' age, they may be so impressed with the theme of the room (and the gorgeous mansion theming/landscaping) that they won't care about your 'better' resort at all. Especially if they don't get a close look at SAB, which is, for many kids, the biggest draw of BC/YC.
Regarding coordinating ADRs and FPs, it's possible to do, if you're flexible. I travel with extended family (my siblings, sometimes my kids, sometimes some of their kids, husbands/wives, etc...it varies from year to year). A core group of us knows early on when and where we're staying. If we don't have enough room in our rooms (lol) for those can't finalize plans until later (usually older nieces/nephews who are in college or in new jobs), we usually get them a room at a cheaper resort later...as the discount we used for our rooms is usually sold out by then. Then, we share what times the early birds have FPs, and the late comers try to make FPs so that some time overlaps between ours and theirs...and we go during that window. Sometimes, if certain people want to ride together, some of us will step aside and forgo our FPs...or in some cases, volunteer to go in the single rider line. For ADRs, we've learned after experience to make them for more than our original party. But when our party size goes above the ADR size, we have one of the later comers book an ADR for a smaller group at the same place close to our dining time. Usually, it works. And when it doesn't, everyone looks at that meal as 'free' time for the larger group to have a break as a smaller group.
Also, you might suggest that your dad and step mom get a RR at POR. At your sisters' age, they may be so impressed with the theme of the room (and the gorgeous mansion theming/landscaping) that they won't care about your 'better' resort at all. Especially if they don't get a close look at SAB, which is, for many kids, the biggest draw of BC/YC.
Regarding coordinating ADRs and FPs, it's possible to do, if you're flexible. I travel with extended family (my siblings, sometimes my kids, sometimes some of their kids, husbands/wives, etc...it varies from year to year). A core group of us knows early on when and where we're staying. If we don't have enough room in our rooms (lol) for those can't finalize plans until later (usually older nieces/nephews who are in college or in new jobs), we usually get them a room at a cheaper resort later...as the discount we used for our rooms is usually sold out by then. Then, we share what times the early birds have FPs, and the late comers try to make FPs so that some time overlaps between ours and theirs...and we go during that window. Sometimes, if certain people want to ride together, some of us will step aside and forgo our FPs...or in some cases, volunteer to go in the single rider line. For ADRs, we've learned after experience to make them for more than our original party. But when our party size goes above the ADR size, we have one of the later comers book an ADR for a smaller group at the same place close to our dining time. Usually, it works. And when it doesn't, everyone looks at that meal as 'free' time for the larger group to have a break as a smaller group.

