You really sound just like me. I finally decided it was time to do another marathon after doing my first one almost 8 years ago. Then nine months after my exciting accomplishment, I had twins! I have tried to do start training for another marathon, but gave up only a little bit into the training. The time was so diffucult to manage. Anyway this is my year. I have signed up to do one in six months. If I am slower, because I cant up in the training time that I used to, then at least I will have done it. Also I love that you said that your kids need to see that side of you. I will use that to help keep me motivated!
Good luck, I hope you reach this goal some day!