Small children will be entertained for a surprisingly long time simply painting with water on a dry patio, path or wall. Just fill a bucket or washing-up bowl with tap water, add some decorators' paintbrushes, and let the fun begin.
Add a paint roller or a squeezy bottle full of water for more patio-painting possibilities. Can the children write their names with the water, or cover the ground completely before the sun dries up their artistic efforts?
They might also enjoy finding a dip in the ground (or using a tray) to make a puddle, then zooming toy cars and trucks through it to make tyre marks. Or using wellies and waterproof shoes to create trails of different footprints.