Any time I do something like this, I give them a birthdate. Sure isn't mine, but it's got to be somebody's. In the case of a brewery, where there is a legal age involved, I can understand the need for a birthday a (very) little bit, but when I'm writing a company about something where there are no legal age issues, I let them know they are out of line. They can ask for an age within a range and I don't have any problem with that.