Playing in the bath, with some food colouring and bubbles in it.
'Washing' dishes.
Playing with rice and containers (put down a big sheet and give them some rice and funnels, spoons, containers)
Drawing
Playdough
Watch a movie with popcorn
Simple board games or card games
Lego/traintracks/block building (If you have some)
Hairdressers/ paint nails (if their mum doesn't mind, and you don't mind ending up with painted toes as well as the nails!)
Cubby house with sheets and pillows over the dining table or lounge
Write a story with them and get them to illustrate it
Tea set with water in it and some small nibbles like biscuits, sandwiches taht they can make themselves
Cooking simple things cookies, make fruit kebabs, make sandwiches, plain biscuits with icing and sprinkles, fairy bread