The oldest (3 1/2 years old) loves being in the shop with me. He's been spending time in the shop with me for some time now. Obviously he's not running power tools yet, but he's been a very good learner about staying safe, not touching things that are sharp or could hurt him, sitting or standing in a designated place when I'm using certain tools. (For example, I don't want him anywhere near the bandsaw when I'm using it, especially with an exposed belt and pulleys and the fact that he likes to brush the sawdust off the stand - don't want him trying to do that while it's running. He also prefers to step inside the house and wait, with the door closed, when I run the loud tools.) He likes stacking wood and being a big helper. If I'm doing something with nails or screws he really likes to hand them to me. Whenever I can actually get my garage shop finally up and running in a usable state I'm planning to cut pieces for some small projects that we can build together. He loves playing with my screwdrivers in the shop - and I've had to go behind him and put a couple things back together that had loose screws that he removed. Yesterday I was sitting at my bench in the lathe area in the basement working on something. He was sitting on the bench right by me, playing with a couple screw drivers and some pen blanks, and we had a good time - he was asking me a lot of questions about what I was doing any about anything in the area that caught his eye; eventually he went to the box of scraps, dumped them out, and started stacking them. Surprisingly this time he actually picked them all up afterwards without even being asked. I can see him taking a definite interest in this as a hobby and as an opportunity to teach him a lot of useful skills that are not being passed on to many today.
The 3 1/2 month old is a little young yet, but he'll be in the shop with me too before I know it and I hope he'll show the same kind of interest in it as his brother has.
I grew up in the shop with dad. I always enjoyed it and I know he enjoyed having me out there. I learned a lot from him out there - both from the aspect of building/fixing things and from conversations about life in general. I really hope to have the same experiences with my boys.