Without knowing the City you are in or the traffic pattern, it is hard to answer. I can tell you that we stay open on Sundays from 10am to 7pm and we do quite well.
In our area, Sunday traffic is slower but the customers that do come in tend to stay a little longer. Get some sports up on the TV's and give them something to do.
For the VERY busy people, the weekend is the only time they have to get out of their weekly pattern and do something fun.