A-1, you should get your grandkids one of these. I can assemble it for you.

hehe

It will only take him 3 or 4 weeks, maybe a month and a half...

Then there's the quality testing to be sure it's assembled correctly...

Two hours, tops.

There was another good toy I played with as a kid.

Mechano, it was awesome to build stuff. I think this and lego got me started with a engineering attitude