I have heard that there are two kinds of objections to the use of Sunday as the effective second voting day. One is the problem with a potential conflict with religious observance and concern that some people may have with that. The second is more administrative—that is, evidently about 10% or 11% of our polling stations are located in churches. It strikes me that the administrative challenge is not an overwhelmingly difficult one to overcome. One could simply look for other public spaces in which to conduct the elections.
On the question as to whether Canadians object to voting on Sundays, I haven't seen any empirical evidence to substantiate that. So the two objections I've heard to using Sunday as the second voting day strike me as things that actually could be overcome.