HI:
Spend time with your kids!!
I was on a development project designing a prototype of a device that eventually got patented and produced.
If anyone has had to do this they know it's not a 9 to 5 experience:your mind is on it 24/7.
My son came into my study as I was ruminating about something and said "Hows your day going"?(he was 6 now 27).
I explained to him in the simplest terms what the problem was and what the device would do.He said after hearing about versions that didn't work, "Why don't you give up?" 
I said giving up never crossed my mind.
He has said that he has always remembered that.
It would have been easier for me to slide in a DVD(or was it a VHS back then) and say go watch this and get out of my hair.
So spend time with your kids.