I too am coming with my family and I've gotten the following information from Americans in relation to grocery for a Family of 4. QR4000 - QR6000. I believe its because of the mix of grocery stores and brands you choose to purchase. I here now visiting for a week and have also noticed for a nice meal for you and your wife in the hotel with drinks will cost about QR350 - QR750. Depending on how many drinks you have. We had a few before Ramadan started so we were on the higher end. Based on those experiences, I've additionally budgeted QR2000 for eating out.
Just like everyone has stated, it depends on your lifestyle but i'd assume you'd want to make it comparable to what life is like in Canada. At lease I do.

I'm here on a visit until Thursday so if you have any specific questions please feel free to reach out to me directly.