Congrats on the little addition, RobboJ! Kids are a blast, you're in for a really fun ride! My daughter is 4 and my wife and I are expecting another little one in August. I can't wait. But, you're absolutely right, they are time consuming. In fact, knowing we have another one on the way has been the basis for my renewed motivation. I know I have to get this done and all sorted before the baby comes or it will be much harder to do so!
That being said, newborns sleep a lot and that gives you a lot of time to get stuff done. An hour or two here and there is kind of tough to get used to, but at least it offers a window of opportunity.
Congrats again, and when you can, post a few pics of your little boy and your project bike!