The way to get two sites as close to each other as you can is to "link" them.
Each site should have its own reservation number. The idea is to call the WDW reservation line and ask to have the 2nd reservation number added as a note to your reservation. Likewise, your friends/family on the second site should call and note your reservation number on theirs.
About 5 days before arrival, reservation data gets downloaded to the Fort for pre-assignment. If "A" wants to be next to "B" and visa versa, a Fort CM will try to make it happen to the extent they can. (Current vacancies willing).
No guarantee of course but give Disney enough info and they should try to get you close.
Looking good so far. My sister checked in yesterday and I called her a few minutes ago and the site next to her and one across is still empty. Keeping my fingers crossed. And for me, its a good thing. My son (12) passed away this past August, so I relish the time I get to spend with my young nieces and nephews.
In the future if you plan to travel as a group, when you start the reservation ask for a grand gathering. Its best to set up all the known reservations at the same time, but they can call then in same day to pay on their own. But the GG number links the reservations together and they try to get you as close together as possible.
I lost my son (29) in November, and I can tell you I know how horrible of an experience you have been going through. Hope you have a magical vacation with your family.