You will not be Costanza (or Kramer for that matter...."I'm out!" ) for very long. When you are ready for a relationship, physical and emotional, you will be snatched up. I am just sorry your wife isn't the one snatching you up anymore.
Her being happy-go-lucky? You know the drill. The relief they feel is false, but they don't see that.
I am sorry that you have to tell your children. That's the hardest part, and actually makes me the most upset when it comes to this divorce.