That sort of thing is quite popular with Boy Scouts and the like. You can get a special magazine for fun father&son activities like The Joy of Spackle. Totally not joking.
http://www.fatbraintoys.com/search.cfm?q=%20bridge%20street%...
Meanwhile, there's little need for toy drywall compound. We have Play-Doh, better in many ways, or for the older and wiser there is papier-mâché or real modeling clay or, well, drywall compound. It's not that dangerous except to your furniture and carpets.
Have we talked to any actual five-year-olds while constructing this metaphor? The ones who are obsessed with Bob the Builder and Thomas the Tank Engine and Wallace and Gromit (tinkerers, ya know) and who own little toy plastic toolboxes and squeal at the sight of construction equipment? Is it only my friends' kids who are like this?
Yes.
Computers are just at the very beginning of revolutionizing the way that human society interacts. Why would you not want your children to have an edge?
In addition, the number of jobs that requiring programing skills is exploding and will continue to grow. The basic idea of automating information tasks is useful for many, many tasks.