If you each have your own ADR, then yes you'll be able to preorder (you'll have to go in each time and order for each party). If you only have 1 ADR though, you won't be able to preorder unless someone's willing to pay the whole thing themself/use all their dining credits (I know doing this is debatable too) etc. You choose your own seats, so you can all sit together or wherever you want, but like you, I had 4 room reservations under my
MDE account to make it easy and they system won't let you book more than 1 ADR for each time period (lunch etc.) on the same day, so I just made the ADR for the total number of ppl. in our entire party (just like I do for most of ADR's), so when we preordered it was only 1 total order and that's why we had to reorder.
You can call and get multiple ADR's for the same time/day, so if that's what you did and you have separate ADR's for each party/room/bill, you'll be fine to preorder.