Entry into a park requires a park reservation for the particular person who tries to enter. If that other party is in your family and friends list in your MDE account and shown as part of your guests in the room, then you can make park reservations for those two others in your party if they already have park tickets for the applicable time period, which tickets have been added to them in your MDE account. You cannot make park reservations for anyone who does not yet have a park ticket applicable to the days you will be making park reservations, e.g., if you have AP's and they only have 7-day tickets, you can reserve a park for them on only 7 of the 10 days. And the fact that you have a park ticket and park reservation does not mean others with tickets can enter with you unless they also have a park reservation.
New APs aren’t being offered for sale right now. If you already have an AP and also have an on-site reservation you can make park reservations for the length of stay and are not limited to the 3 days for APs not staying on site. We have APs and reserved 10 days worth of park passes for our Dec. DVC stay.
I’m not sure what your second question is, we do have friends joining us for a couple of days staying offsite & after they bought their tickets we reserved their park passes for the same parks that we had those days. So if your other party has APs but are not staying on site they’ll be limited to 3 days park reservations at a time, I believe. Otherwise as soon as your other party buys park tickets they/or you if connected via MDE can make park reservations for the same parks you have reservations for.