I am having an outdoor wedding at my parent house this June. We are having an open bar with beer and 5 hard liquors plus soda. We will be having 2 bar stations and 4 bartenders. We are paying them a flat $75 for the night (8 hours) plus feeding them and splitting tips. I am wondering how I should word tipping to our guests. I will be posting a list of drink options on the bar top for our guests and wanted to add something at the bottom regaurding tipping. Any suggestions?