Hi HeavyD, I don't have any great insights, but I wanted to let you know I keep up on your sitch.
Your feelings of pain are valid. Your feelings of missing out on a fun time with your WW and kids are also valid. You are not being small or a jerk for having these feelings.
On the postcards, what if WW had not sent the postcards, would you have felt better?
It seems that you should take the postcards at face value - that your children missed you, they expressed this to their mom, and she made a simple gesture by sending the postcards to make sure that you knew the kids were thinking of you.
I am not sure why the postcard was sent to your mother, but again accept it as a thoughtful gesture, and nothing more.
Any way to make it hurt less? Ha, if you have the secret elixir for this, please share it with all of us. Sometimes things just don't make sense, and there is no way to get our heads around them. That is why the DB program preaches detachment and GAL. In this, what WW is doing eventually becomes less important to us. Best wishes.