You're allowed 1 companion. Although sometimes the gate agents will be nice and let you have 2 companions. But to be really safe, you could call UA and ask them how much it would be to bring a 2nd companion with you.

I believe you'll get Seating area 1 if everyone is traveling on the same PNR.
Anyone who's not on your PNR but associated with you (not sure how UA accomplishes this) will probably get Seating area 2. At least that's how it worked when I took my friend to SFO. He was on a different PNR I believe so he had Seating 2, I had 1. This time I had another compantion on the same PNR as me and we both had Seating 1.