Sigh. In the old days, you could have called it an "amateur night" and that would have been just fine. But that has come to mean 1) some undertaking that has been completely screwed up, or 2) binge drinking sprees on certain holidays, or 3) special nights at strip clubs where the women in the audience get involved, ... and probably a few more horrors I'm not even aware of.

"Talent show" might also have been an option, except that has come to be strongly associated with competitions (Miss America, etc.)

I think that leaves you with just "show" or "variety show." You can add "amateur" to make clear it was informal, or you could express that in some other way: "... which was read aloud during the variety show we put on for the March 8 holiday."