Hi Mark!!
I believe that you very well know your wife's actions speaks for themselves. She is adventuresome, yes but she is also, like you afraid of being alone and in order to avoid ending up alone she gives you a story so you will not leave her despite her being with another man. You in your turn refuse to see what is clear to everyone: She is plain being unfaithful, that is the truth, the reason she has for that is a diffrent story. In order to avoid facing a life on your own you put up with your wife being unfaithful and only you can decide if that is ok for you or not. In a way this is life finally putting you on the spot and giving you a chance to develop into a free man using your wife in provoking you to take the step into the unknown. You daring to live on your own is you key to "freedom" (freedom in the sense of being in charge of your life).

You are scared of a possible life as single but , honestly what is the worst thing that can happen?? I seems to me that your behavior circles around avoiding ending up "alone" and rather than letting that happen you contiune to put up with a life that for a couple of years now has been very difficult to you due to your wifes urge to be adventurous. You are being treated the way you are because you allow it!! Do you really need a person in your life that clearly hurts you? Are you willing to suffer any longer in order to avoid being single?

I have gone through pretty much the same myself and in order to avoid being single, wich was my biggest fear, and rescue the children from growing up in a split family I endured (I allowed)
pure hell in my marrige for years. My husband finally left me and after he did so I realized life as a single mother was peaceful and happy and my only regret was that I put up with my husbands lies etc for so long.

There is no rewind in life and if I were you I would accept what your wife's actions tell: She is off with another man and she would not be unless she wanted to and you can not want to be with another man if you are married unless you no longer have the comittment to your husband and love for him. Mark, grab life and start with facing your big fear: Being on your own. When you have overcome that fear you will be free to chose your partner in love as a free man as opposed to being a man that settles for less in order to fight off the fear of being lonely. Your wife is aware of your weak spot and she plays on it because she is just as afraid as you are for ending up without a partner. I believe she would not hesitate to leave you should a man attractive enough for her want to marry her, that is she could go from your marrige directly into a new marriage.
Again, what is the worst that can happen?

As for the children my experience is that divorce is difficult for them but you can make it easier by refraining from backtalking eachother. Eventually they figure out for themselves who their parents are. I can not enough emphacise how important it is to stay away from ventilating disapoinment etc to your children, let them keep their idealized version of their parents that they need to have.
Wish you all the best ! And remember no pain no gain. This is your chance to take charge of your life!!!
Best regards Mbarsk