Totally worth it. You have the right idea and the right mindset. The journey is the best part. finishing a car is awesome, but getting there is perhaps the most fun of all!
I just turned 50, have a year and a half old son and another on the way... I intend to keep up with the hobby albeit at a bit slower pace. I hope I have the stamina to do with my son (s) what you are doing with your boy someday.
I am on my fifth resto and have kept them all. They become part of you. I have never regretted - not for a single moment - the money I have spent on any one of them. Don't ever regret, lament of second guess what it is you are getting started on. You will come to love every moment of the journey and look back upon completion with rewarding memories, newfound skills, new friends and a hobby that will never let you down. If there is one thing I did learn though is that the more I can do, the better the experience. More than one body shop frustrated me in my early days - before I honed my skills at rust repair and bodywork... now, I do it all myself (except color) and am able to save myself a significant chunk of change.
Enjoy!