We didn't see a service fee or gratuity charge on our catering bill, which we have already paid prior to our wedding this weekend. So, I'm guessing we should tip. However, we are having a buffet with a few appetizers being butler passed. I'm guessing there will be 2-3 butlers passing appetizers for 30 minutes and I know we have 2 bartenders for two hours. I'd think 18% of the total food and beverage bill would be a bit much, since we aren't sitting down and won't have waiters. Any suggestions? Maybe 10% of the catering bill? Or just tip each butler and bartender? And perhaps the catering manager/coordinator who is on site?