Fucking hell, your life is YOUR life, your kids and mom will understand. Heck, they probably already perceive that something has been amiss for a while.
It is great that your kids are older, you don't have to fight over custody and time spent with them. Starting over means that you get your life back, not be some husk of a stuck human that just goes through the motions and has to deal with a crappy loveless marriage.
Don't beat yourself up over naivete, it is so cliche. I did the whole "How could I have been so stupid" phase, and although I still think that, I don't beat myself up anymore. It is all just a snapshot from a time when you were dealing with the hand that was dealt to you. Now you have a different hand, plus you get to do some dealing of the cards yourself.
You are fun, not dirt poor, and nature hates a vacuum. There are plenty of chicks out there in the same boat, go play the field a bit and start choosing who you want to spend time with voluntarily for a change.