Regarding 5 in a unit: if one of your kids is under three, they don't count towards the four-person limit---the 1BRs even have Pack & Plays in them, IIRC. If everyone is three or older, offiically Disney won't do it---and if you call CRO asking to book five on a cash reservation, they won't even discuss the possibility.
However, Member Services has been known to allow Members to book five into 1BR units from time to time, quite unofficially. Keep searching for a 2BR, but if you are offered a 1BR, put it on 24-hour hold, and then ask the II agent for the Disney reservation number. Then, call Member Services with the number and ask them if you could put a fifth person on the reservation. The worst they can say is no, and you can cancel the unit, resuming your initial search. But, you must cancel within 24 hours---not the end of the next business day, but 24 hours.
You don't want to put five in without telling them. You won't get a fifth KTTW card for EMH, and you won't be able to use ME.