According to Apple forums, there is currently an issue happening with iPads involving audio. The last iPad I worked on with this issue had fixed itself once I turned the iPad off, then on again with the dongle and headphones still plugged in. Doing that seemed to repopulate the option and made it selectable. If you could please try this, I’d appreciate it since troubleshooting further will require me to take all of the affected iPads and I don’t want to disrupt your plans with them. If it doesn’t fix the issue, please let me know and leave any iPads that are affected by the problem off to the side along with their adapters for me to grab in order to troubleshoot further.