I would say to offer to help with transportation for the kids, like do you have to provide your own transportation to preschool. Housework would be great. I helped a lady on bedrest with twins once, and it was hard for her to ask people to clean the house. She kept saying, the bathroom is what needs cleaned, but I don't want to ask that everytime you come over! Maybe check on the 9 year old and see if that child needs help with homework etc..
I have been sick this week and my son needed quite a bit of home work help and it was hard to have patience with that. My DD who is 12 ended up helping him for me.