Here’s a great starter lesson with geoboards: figuring out the area of squares and rectangles.
In the above picture I threw in some square inch tiles so that it is really easy to figure out the area of the rubber band square, just by counting. This also teaches early multiplication skills because we are looking at a 4 x 4 array.
Here’s another example, this time with a rectangle. To find the area of this rectangle kids can count the squares or…
…They can transition into just multiplying 2 x 4.
So now we’ve got an activity that teaches shapes, counting, area and multiplication all in the same lesson. You could do this with your four year old, or your nine year old, and they would both get something out of it.