Most Helpful Girl
Personally I assume that any time a man asks me anywhere it's sort of a date. Two people going somewhere who would otherwise not be going there together to me is a date. If you want her to know for sure that it's a 'date' and not a friendly hangout, at the end of the night just say 'thank you for an awesome date' or something along those lines. You could always reference it in the beginning of the night, something like 'I've been really looking forward to this date' or whatever works. If she goes with it then you've got your answer. If she didn't think it was a date she'll likely say 'oh I didn't know this was a date'.