Any STEM profession requires agility and resilience. An obstacle course builds both traits at once. Plus, it's just fun. And, you don't have to tell your little competitors that there could be math involved in the scoring. Or, if you want to get really tricky, you can make one of the challenges a math facts challenge. (see tips below) Shhhh...we won't tell if you don't.
You can do this inside or outside...depending on the weather. The links below with give you some thought starter ideas.
Project Materials List
Paper for keeping track of scoring
A watch or a clock for timing the competitors
Common household items (e.g. a broom or mop, string or toilet paper, furniture, books or bricks, etc.)
Related Web Links
Check out this web page for 25 different ideas to create a low prep time obstacle course.
(Note: The link is one of those pages with a bunch of ads running and flashing on the sides. I hate that, but the ideas are really really good.)
Ideas, Notes, & Tips
You might need to help the kids get started, but back off once you see them want to take over. Leadership qualities are great STEM characteristics to nurture in a child.
Let them make mistakes. Mistakes are important elements in the learning process.
You might think about getting them prizes. First, second, third place, etc.
Throw them a curve ball by introducing a math fact obstacle in the middle of their physical course. There's nothing like having to stop and do you 7 times tables to spice up the game a little.