Originally Posted by Mike:
2 of the 3 kids at my workshop yesterday were 4 and they had lots of fun assembling the birdhouses.
Your post just gave me an improvement to my idea.
I was planning to sell my workshop projects in the store for parent who would like to take them home to build with their kids there. They would be great ideas to sell to daycares. How many birdhouse projects do you want? 
My mom did a birdhouse with my dd4 over Christmas break and she was SUPER into it. After they assembled she spent like an hour painting it.
I second the "project" idea along with lots of outside. The project could be as simple as building a city out of legos. Give then one step at a time, build a house, then when they've finished, ask for a play ground, a school, etc....
Also we've just gotten into scavenger hunts. I draw (or print off) simple pictures (the fish tank, the fridge, the cube shelf) instead of words. The last one I did I made sure that if they were upstairs the next thing to find was downstairs and vice versa. 10 or so trips up and down the stairs burns some energy
. A small candy or treat prize at the end. The bonus was then my dd spent a good bit of time recycling my clues and re- hiding them for the other kids.