Don't have kids, so pinch of salt this - but my dad used to make "golf ball runs" for us when we were kids. Essentially long, elaborately set up contraptions th

Don't have kids, so pinch of salt this - but my dad used to make "golf ball runs" for us when we were kids. Essentially long, elaborately set up contraptions that you put a golf ball at the top and it rolls all the way to the bottom, dropping through pipes and rolling down boards. I'm 40 this year, I still remember this vividly. I guess marbles would be too edible (ha), we always did this outside (fresh air), we were building things, and I just remember it being magical watching the ball _finally_ go down. And then two balls, and then three... I'll second Duplo - that was my precursor to Lego, which was my entertainment for YEARS (before I found computers, anyway).