think you should have a break from your missus and this other woman... it would be good to spend some time with yourself rather than shack up with the first bit of excitement in a skirt that gets the hormones raging.
To leave your missus for another woman is devastating and not fair on anyone including the new bint who will be seen as the man snatcher or the kids..

Personally speaking things like this rarely have a happy ending, you need to think about your position with the kids, if you intend to let them carry on living with the missus you will ultimately miss out on some of the growing up of your kids... and how will you feel if she meets another fella and takes them into the family home..

What happens if your young bit of skirt wants kids in a few years... how do you feel about that ?

Personally it sounds a bit midlife to me...... See you on Trisha