Meg - my situation is similar to yours, my kids are younger and A started when I was preg the 2nd time. Your H is quite possibly still seeing the OW - He's going to be really weird for awhile, maybe forever. Keep an eye on finances, watch for strange transactions. Keep in mine the solution/resolution you want, but don't let yourself get blindsided since you have 2 little ones to watch.
Teratosa has a similiar situation - hers is so far working out, but she's over a year into this.
Faith is, at one and the same time, absolutely necessary and altogether impossible. --Stanislaw Lem