Michael,
Can I be one of your kids!?
Elizabeth,
I think balance is one of the toughest things to accomplish in all parts of life. I think a good way to gauge things is by living without regret.
You don't ever want to spend so much time doing family things that you get further down the road and look back to only regret that you didn't make more time for your art and your own interests. That tends to create resentment towards loved ones, even if you don't feel it at the time.
But you don't want to work so much that you get to the point where your kids are gone and you regret that you didn't spend enough time with them. If you can find balance you are way ahead of most.
I don't even have kids and it's hard for me to justify spending more time on my art than going out and having fun with friends.
(Ooops, some big help I am! Guess it's a struggle for all of us)
Best wishes finding the balance! Take good care!