Table Top Children's Art "Canvas"?

What can I use to color and create on a white glazed tile table top that can be water proof and removable? I have a kitchen table with a wood border and 4X4 white glazed tiles designed in the center of the table; there are a total of 15 X 8 tiles. I would like to color or paint on this table and use it as a canvas that is re-usable to display my grandchildren's art in the front yard. It must be able to live through the rain, but be able to be removed when needed.

By Anita J.