helping-out the service industry

Sometimes I can cause a little embarrassment when we go out - when I tell the people it's my birthday, when it's really not.  On the occasion, I might get a dinner coupon, or at the best, a meal half-off.  That way I can double-up on the tip for that 'poor' server, just to compensate.  But, my wife doesn't always understand the thought or the embarrassment.