Why require the "sit down" part? As the article states, you can do math without sitting down, too.

Let them estimate how many steps a walk from A to B takes, or what distance is larger and check it by walking, ask them to count how many tiles cover a square (multiplication as a fast way of counting every tile), to estimate the number of beans in a jar and from it the weight of a single bean (combine that with Archimedes' law and let them predict whether it floats), the height of buildings (3 to 3.5 meters per floor, but also a trigonometry exercise when combined with measuring the length of its shade) etc.