If you are booking them with your miles, everyone will show as having your status, and thus have access to E+ and your baggage allowance even if you are not on the same PNR. If you are mixing revenue and miles tickets, you cannot put them all on the same PNR, since everyone on the same PNR has to have the same fare class.

However, miles tickets are not upgradable (unless you have one of the newer UA Chase cards...not sure which ones), and do not earn PQMs. Therefore, what I would do is book my ticket (to get PQMs and my upgrade priority) and the ticket of my wife's favorite child preferred underage traveling companion on one PNR with cash, and then book the rest with miles. Be sure to seat all the miles tickets together. Then, if my upgrade cleared, I'd give my wife my upgraded seat. For bonus points, book only your ticket with cash and ride with all the kids in the back (remember, she's at home with three kids while you're zooming about in F).