I know this is an old thread but I was doing a search to help myself and this is what is says on the CRA website under claiming "Other Expenses" for home daycare.
"It is often difficult, for example, to separate the cost of feeding your own children from the cost of feeding the children in your daycare when all groceries are bought together. This is also true if you do your own laundry at the same time as you do the laundry for the daycare.
As long as the other expense is related to your daycare activities and is reasonable, it will be allowed."