Add click-to-call buttons to your mobile ads. While the behavior will have to be extrapolated somewhat, you should still see an increase in store traffic. Encouraging calls adds that valued human touch.
Conduct a survey from previous customers on the following topics: favorite cake flavors, dessert preferences, favorite cake recipes. See if store traffic increases after the survey has been issued.
Incorporate some geo- or A/B testing into your marketing plan. See how different people in different regions respond to your display ads. Choose the most popular ad to base your next campaign.
Establish a baseline of store traffic before the campaign. Release display ads when you know your customers are most likely to be online. See if store traffic increases after display ads are released.