May I....

That's so polite I don't know if I can say no

That's both elegant and practical for shy ones, bonus points for quirky and smile-giving.
By the way what's the font for the first and last lines?

-by fall out boy

Buy how would you know if they are standing you up? Seems like it would be better to get the card back for yes and keeping it for no.

*Gives card*
*Runs away before they can even read it*
Date garanteed

Would say yes just because of the forethought.