Texaco is underwriting the Wynona Judd tour. A couple of years ago, they did the same thing with the Beach Boys. The customer gets discount coupons at Texaco. This made nationwide headlines. A ticket or coupon cane let the customer in free or at a discount.
Many tickets work well on events with low admissions, maybe two dollars.
You should confine your cross-promotions to short periods of time, preferable one week or two. Employees get tired of working the promotion and soon start losing enthusiasm. The coupons should be dated to expire in a month or two or sooner. As far as a small business, every fund raising cross promotion should be local. This really brings the event home much more so than in a national or international effort such as money for kids in far off country.