Ava - please don't do this - I know your heart's in the right place, but bribing for business makes you look desperate and unprofessional. And it's not likely to work. If you really do want to try this approach, do it with strangers, but don't risk your credibility with your sphere of influence.
As far as to whether there are any legal implications, I don't think so. If you were offering cash, there would be, but as far as I know, a gift certificate or gift card is fine.
_________________________
Jennifer Allan, GRI
RE/MAX Hall of Fame
Author of
Sell with Soul, Creating an Extraordinary Career in Real Estate without Losing Your Friends, Your Principles or Your Self-Respect