I don't really have an answer on the question, I am just another person starting out on freelance and struggling at the similar situation. I have a kid and a fulltime job as well. So I guess I am on the similar situation as yours. But I am already 37 ;-)

I tried not to sacrifice my time with kid and wife so I tried to wake up earlier at 4-5 a.m., spend 2-3 hours to work on things, then go to my fulltime work. I find this time of the day work better for me than if I stay up late to the night. You are alone, the air is fresh, and you are like having the whole world :-).

It is not easy, sometime I just couldn't wake up that early after the alarm went off. And then feeling guilty the whole day for not able to achieve the thing I plan to do. Sometime the alarm wake up my wife instead of me, and she couldn't fall asleep again after that, that is also a big problem.

I think focus, persistent and discipline is important. When we don't have the luxury of spending the whole day on the thing we need to work on, break a big task to smaller chunk that we can complete in shorter amount of time. Focus on small steps instead of climbing the big mountain.

I post about my story here as well http://www.kahfei.com/?p=242. A long post though.