Are pre-purchased tickets for specific date and time. I purchased them, but won't be going for another couple of weeks.

I don't think so. There are no schedule tours. You can come and go as you please.

Suggest calling them.

I don't have an answer to your specific question, but we bought tickets at the front in the gift area. It's a self-timed tour, but they do have scheduled showings of the film they show. I can't imagine there being a sold-out timeslot, unless it's a specific special day. I think you're fine, no matter which way you go.