I have hosted tea tasting using gaiwans many times. They are good tool. I remember the article here says using tasting mugs, but gaiwan is cheaper and easier to get. Use chahai to pour the tea into for study and holding the tea. Use small cups or Chinese style porcelain spoons to drink from. If you are beginning, 3 or 4 tea(s?) is good. I think it is better to practice preparing these 3 or 4 teas at the same time before actual tasting with the customers is important.
I don’t know your customers so I cannot comment on tea choice.
