You have the ultimate incentive in those kidlets of yours! I don't know about your job situation, but I have started using a stability ball
at work in place of my desk chair. It exercises the core, I am in constant motion and I do crunches, stretches and other strength building exercises naturally throughout the day. The added bonus is that they cost about $20 so they won't break the bank!
I encourage you to get your Sparkpage up and running. It allows others to 'friend' you and to give you personal encouragement and support.
Also, consider joining a Sparkteam (or more than one)! Here is a link to teams that are family focused. www.sparkpeople.com/myspark/groups_categor
There are many more, so start exploring!