Few questions about food and taxes

[SongSparrow]

I think it actually would be fine to make an estimate as long as you know you are within reason. If you have a set up where you buy groceries separately, store them separately, cook separately from your family then it would be easy to calculate an exact cost on your tax return. If you don't then it would be very time consuming to come up with exactly how much you spent. For me, my time is worth more than a bit of extra money I may be able to claim, so I make an estimate that I know is reasonable.
The CRA says this:
"Other reasonable expenses
It is often difficult, for example, to separate the cost of feeding your own children from the cost of feeding children in your daycare program when groceries are bought together or if your
own laundry is done at the same time as laundry used during the course of business.
As long as the expense claimed associated with these daycare related activities is reasonable, it will be allowed."