My assesment of the situation is this.
Would I take her back ? It depends if I could forgive her for what she's done. If she was drunk then well maybe, everyone makes one mistake. I could probably forgive a drunken one nighter mnore so than I could a premeditated bonk.
Lets be honest here, she chose to do it she wasn't forced so she can't really be all that into you mate. I know you've got a rep on these forums for shall we say making some silly mistakes with the ladies and I'm not judging you by this at all.
Think to yourself, if she's done it once (and thought about it) then could she do it again ? No matter how sorry she says she is, or how much she says she loves you, you will always have that doubt at the back of your mind. You'll always be wanting to know who she's seeing, who she's going out with, before you know it you'll be checking her phone.
See where I'm going with this ? There's no trust, you can't have a relationship with someone if you don't trust them. I'm not going to go into details about what happened with my ex, but it got the point where I couldn't trust her any longer and made the hard decision to walk out on her in my first proper place away from the family home.
It hurt like hell, but it gets better. The pain goes away, you realise that you can live without her and that there is someone else out there thats meant for you. Take some time out mate and enjoy being single whilst still being a good Dad to your kids. Life is stoo short to get yourself tangled down with all this emotional bull crap.
Seriously not worth all the agro and stress, get out now and save yourself even further pain and suffering.