If you're doing a startup, you probably have more flexible hours. What I actually do is start work around 4 or 5 AM and finish at about 3 PM. My family is not awake so I don't miss any time with them. Less time on commuting, finding parking, etc, and plenty of time to work. And I have huge gaps of time to play with my kids.

But if possible, I'd recommend finding a way to work less hours. I find that lots of scheduled time kills a lot of opportunities.