My boys are still pretty young but that does not mean they are too young to start working in the shop. One of the reasons I started this business was to show my kids how to make/build things.
I'm involved in some other business ventures (investing & finance) that make it hard for them to see and understand the concept of working, building something from nothing, finishing a project, using the thing you made, etc... Building tables makes sense to them. Stocks, bonds, and spreadsheets do not 🙂
Personally, I like them to work with real tools and real materials. Some toy tools are o.k. but most of the time they are just junky plastic products that don't really teach them anything that they can use when working with actual building materials. This is often hard for me. They make messes in the shop, get glue everywhere, and make my cleanup twice as long. But they are slowly but surely gaining skills and real world experience.
There are lots of fun things you can build with your kids...
My boys and I recently made this kid-size workbench. We made it out of shop scraps and while I did most of the cutting and assembly, they did the sanding and staining all by themselves. Yes, They made a mess and got stain everywhere, but in the end they now have a REAL workbench they can call their own.
I also teach them how to respect and take care of their shop space and tools. Putting things away after use, sweeping up messes, etc... These are all things that will serve them well with whatever they end up doing in life.
Young kids are much more capable than we adults think they are. Sometimes you just need to step out of the way and see what they can do. You might be surprised what they make!