Definitely want a pergola. It's a big winery in TX - also an event center so it HAS to be a perfect, beautiful show-piece. Lots of wind, sometimes sustained winds of 60mph.does the client really want a 'pergola' or just a covered space for employee picnic's? That latter is just a pole building with the roof made out of trusses-a barn without walls.
where are you located? CA has their own set of requirements, up north has snow load, down south may have more wind load to consider, all things the engineer will be able to evaluate while drawing up sealed plans to build from.