When it's nice outside and there are a few moments before dinner is ready, I take the kids outside with a small bucket of sidewalk chalk. In order to make the chalk more velvety, I add water.Just soak chalk pieces in a bucket of water overnight or as long as you can before using. I also pour the water on the sidewalk to wet it and let the kids draw. Wet sidewalk chalk has a smoother texture and the colors are more vibrant than when used dry. We also found this suggestion from Scrumdilly-Do blog - add a cup of sugar to the soaking water to make the colors pop even more. We've never tried the sugar trick but it sounds interesting.
Image: Scrumdilly-Do blog