For whatever it is worth, we had a large party of 15 for a December visit. 4 of us are AP, the rest are not. This group consisted of 4 different families with each family having a separate
MDE account. We were all staying at BLT in 2 rooms (3 bedroom & 1 bedroom). All of us, except one who joined last minute, were listed in the DVC reservation in the 2 separate rooms. My biggest challenge was getting everyone to show up in my Friends and Family list ("controllers" of the MDE acct were showing up fine but kids were not. Had to work with MDE chat to resolve each time. Luckily I did that weeks in advance of trip). We were AP but everyone else went ahead and bought tickets with Genie + option (can't do that with AP at this time) and we all selected the same park reservation. When I woke up at 7am each morning and went to select Genie + for our group, everyone showed up. I then selected all and made the Genie + reservations for our full group. Again, 4 had AP, 11 had regular park tickets but added the Genie + option when they bought those regular tickets and we all had the same park reservation.
The only issue we had was the person that joined last minute was not listed in the DVC reservation at BLT. So when I went to purchase a ILL for Rise, I could not select him at 7am. I could get him Genie + but not the ILL. At least at that time in Dec you had to be a resort guest to have the ILL purchase option at 7am. However, I had no issue selecting AP and regular ticket holders together for Genie +. I heard stories of glitches too but for whatever it is worth we did not have that experience.