Am looking after niece and nephew for the day and night and had planned lots of outdoor stuff to do with them and ds (1) but it's going to be bloody rainy. So ideas so far are:
making play doh which they can then help ds play with
baking a cake (while he sits in high chair and watches)
bit crap, everything I can think of that they might enjoy involves poor old ds sitting in high chair or pram out of the way.