2 files, how long would it take to change OR a file with 2 slides and the keynote looped. One slide with the info and one slide with the closed message OR 3 slides, the first and third being the same so just one file opened each day and tapped twice. It's not automatic, just needs someone to remember to move onto the next slide at the beginning and end of lunch, but it would do the job 🙂
Daz