I know you can preorder for breakfast and lunch. Are you all on the same DDP? If so then yes, place it all on one order. If not, then you have to split it between each DDP.
Okay, this gets a little complicated. Is your ADR for ALL of you or do you have separate ADRs? If all of you are on the same ADR and you preorder, all the DDP credits will come from ONE room. They will not split it up into "this is yours, this is ours." All meals will come from one DDP "account." So, if you're going to eat all your meals together anyway, then you just take turns "paying" for them. If you're not comfortable with that, they you either need to NOT preorder or you need to make separate ADRs all around the same time, so you can enter and eat together.