I say ... let them jump in puddles!! (That's really not very helpful, is it - sorry!)
My older ones like inventing their own board games (huge pieces of paper, lots of pens and imagination) and you might need to supply the dice.
If you have a big enough roll of paper, they also drew round each other and made life-size "models" of themselves - using various bits of material to make their clothes (just glue it on), wool, foil, buttons etc.
They also like being let loose with a huge box of "junk" (parents often comment that I basically collect rubbish which I allow minded children to glue and take home!) We keep big boxes, and had enough to make a five foot tall "robot" once. It lived in my hall for months.
You've already mentioned cooking - you can do that more than once (even easy stuff like decorating biscuits, krispie cakes, making packet mix cakes). Get them to make playdough as well!
Mine are allowed limited time on games console, particularly if it's raining.
We will probably go for a roll in the mud in the woods, colds or not!