Could I suggest that you have an obvious Tab or Link on your homepage advertising the sunday openings.
A few people I have mentioned it to couldn't find the info, and thought it was a private collection.
Unless you know to look in the forums, it is not easy to find out the info for newcomers.
A few people have asked me if they can use the machines! They thought it was a static display with just a couple of items powered up when not doing the shows.
Also, may be worth having a "We are Open this Sunday/ We are not open this Sunday" message box before people book tickets.
Hope this helps. Keep up the good work.