commiting to half marathon

I'm officially registered for the Chicago half marathon---felt like I had to commit the $ if I was going to commit to the training---at least it will be flatter and warmer than Mississippi Blues half marathon in Jan (God, that was awful!).  Ran 4 miles today on the treadmill---hate the treadmill, but it's been too rainy to do anything else.  Hoping this second half marathon will get me ready for my first full marathon in December---Jeff promised the kids he'd run a marathon by age 50 and wasn't able to keep that promise.  I'm turning 45 in October, so I'm a little ahead of the game, but would rather do this now than 5 years from now.  This hasn't ever been a goal of mine, but I guess I want to make good on Jeff's promise, show the kids that I'm healthy and not going to leave them, and give myself a goal beyond managing to get up each day, breathe in and breathe out, and try to be an effective mom, teacher, clinician, etc.....this one is more for me.  I'm commited to making myself the best me I can be and leaving it up to God to figure out what happens from there.  Trust in God---that's what I keep telling myself.