The name itself in the form of a question; for something unique looking and somewhat humorous, such as:
I can has cake?
And then your names:
Syd&Carol
People that enter your shop, are entering for cake, the shop name "I can has cake?" is funny and does not deter the customer, but somewhat attracts them, as if you already offered them cake, and they reply in happiness "I can has cake?"
The "has" as opposed to "have", makes it even more humorous.
You can also add some cake propaganda to make it look attractive.
Cake itself is a luxury, a celebratory food, and I think this name as a question makes it fun.