How does that work with being a parent?

I generally work a very strict 7:20-4:20 schedule and my "extra effort" is usually taking a short 20 minute lunch when I get an hour.
But sometimes we have a big deadline and the partners will ask us if we're able to put in OT. I usually want to try my best because I'm vested in the project. I'm not able to stay late so I'll usually put some time in remotely from home.

How do you balance the requests for OT with parenting?