What special activities to do on a snow day?

It is a snow day today. All the kids are home from school. I have 3 biological kids(13 yr old girl, 10 yr old girl, and 7 yr old boy) and 3 foster kids(all boys 10, 8, and 5) The 5 year old is autistic. I want to do something special today. My husband is at work but I am a stay at home mom. This morning we got up and went sledding on a few hills by our house, then came inside and had hot cocoa and lunch. I was thinking this afternoon we could do a project of some kind or something else special. Any ideas for kids 5-13 years old?