Sorry you won't be able to join salomonsson :( but for others reading this:
To be clear, Moss's interaction scheme is a great example, as long as your hands can generally stay within your tray table area. It's totally fine for game's visual action to go outside of that, as long as you don't have to turn in your seat to see it.
Keep in mind a major (albeit somewhat downplayed) thrust of this jam is accessibility--and the ability to actually finish a VR game in a weekend--much more than the literal smallness of the game (though i think the idea of teeny games is still a lot of fun). Immersive worlds are all-the-better!
And to you salomonsson, I hope you take this inspiration to make your own Tray Table VR game and spread the word! Keep an eye out for the next one!