You have to know what has gluten and what doesn't before you order - don't expect a minimum wage ever changing staff to go out of their way to research gluten sensitivity for you. Ask about the individual ingredients for your concoction. I'm celiac and I had the peanut butter banana smoothie, 4 safe ingredients, with no issues.
Pinkberry is a great treat in terminal D of the Charlotte Douglas airport! They have a GF list you can read from (I looked on the internet) and the Greek yogurt is GF but the frozen yogurt is not... Lots of the toppings are GF.