Number Spider - Draw a spider. Then choose a number between 0 and 20 and place it in the middle of your spider. For the legs, think of as many different ways as you can to make that number.
How far can you throw?
Throw a bean bag or soft toy. Measure how far it went using non-standard units. Remember, non-standard units can be anything as long as they are the same. Do not leave any gaps between your non-standard units.
Human Number Line - use chalk to create a number line (0 - 20).
Get a grown up to tell you a number. Run and stand by that number. How many tens? How many ones?
Repeat with different numbers.