The venue that I chose has a wedding planner that will coordinate all the aspects of their venue -- they will do all flowers, reception lunch, cake, musicians, etc. Since I'm not paying a fee for her, but she's doing work on my behalf, I'm planning that I will need to provide some sort of gratuity for her help. What is customary in this situation? Is a percent of the wedding venue cost, or a flat fee? Any suggestions, thoughts?