I wouldn't involve OM family.... from my own experience they might not care. I never anything to OW family (mom/dad/siblings) but she and my H told them he was married with me being pregnant & they welcomed him with open arms. It may not work out like you think...

As far as telling the kids, I would talk to them about how marriage is really hard work and you're doing the best you can right now but things are rough. Assure them that they will always come first but mom & dad need some space. So they can see W sleeping on the couch & not get upset. And no, I don't think it will be easier once the kids know. I think reality will SLOWLY set in.

Me: 35 husband:39
Sons 16 and 11 from my first marriage
Twins 5 (boy/girl)
Daughter 3
Affair bomb 2/27/14
He moved in with ow 3/13/14
OW kicked him out 6/15/14
4/2016 he seeks help for sexual addiction