The boy also wanted a "big red garden" and proved he could take care of it with a smaller garden we built for him a couple years before....so, I told him to bust out his notepad, draw up what he wants, then we'll transfer it into legit plans/measurements and transfer that into getting lumber then build it...of course we had to do it together but it was complete over the course of 2 days and the most expensive thing was the potting soil (like 25 big bags when all said n done) I think all in I spent 500 bucks and it should last a while ....the best thing is that this garden has been up since early last spring and everyday he tends to it and takes care of it....now it's expanding and will be gated in and act as a tortoise pen with a tiny dog house and whatever else he comes up with in there, this is "his area"....for my money and what we spend on these stupid trucks less than 500 bones to give the kid years of entertainment and learning to garden for himself is a win, I am pretty hands off with it at this point, little guy handles everything and we actually do eat out of it.
The kid has proven to be quite a greenthumb, it's relatively cheap, and we find alot of after school projects to get into related to this kinda thing. Here's a few pics of random stuff he has done....maybe give some of the cool dads on here some ideas.
I think the main thing is to just be patient and look at everything as a learning opportunity and include them, this kid gardens, does concrete, rebuilds carbs (take it for what it's worth), welds (kinda), built my shitty shed with me (that I don't have a finished pic of), and does yardwork like a boss, he even ran the excavator with me and was my rock hound when I was grading and redoing the driveway... fatherhood is one of the most amazing things ever, and it doesn't necessarily have to take a lot of money to do diy stuff with the spawn, as long as it's safe, why not include them.
I've accepted the trucks just aren't going to get finished quickly, he doesn't have an interest in it really and my time with him is split 50% so I try to capitalize on the things he is interested in and make the most of every minute, it's exhausting and hard but good golly it's amazing.