Determining the optimal allocation for multiple individuals is extremely complex, but it is a solution we are working towards for many of our current and future solutions.
To navigate towards the optimal answer, I recommend ensuring all individuals are in the same tax bracket (both Federally and provincially) and are taxable (i.e. all credits have been used). You can easily do this by reviewing the tax bracket details at the bottom of each worksheet (if you're using the "Standard" versions).
There is a function in Excel called "New Window", simply go to "View" in the toolbar, and then select "New Window". This will allow you to see two parts of any worksheet on two different screens. It's very handy for this type of exercise.