This is a highly contested area of law. If the payment to the servers is really a service charge, then you can take a percentage of the service charge and pay the sales staff. However, you need to make sure the "service charge" is not considered to be tips. You also need to confirm your servers are making minimum wages. Most cases hold banquest events typically charge a mandatory service charge. This is a very dicey area of law and I strongly recommend you contacting an attorney who represents employers. Unfortunately, I only represent the people!