The question of whether to bring your phone to a demonstration is a personal choice, because they could be subject to electronic monitoring, but phones may be deemed worth the risk based on the needs of the demonstration.
Discuss this issuewith organizers beforehand
If you decide to bring your phone, disabled all fingerprint or facial recognition unlocking features and instead use a strong numeric password
Familiarize yourself with your organization’s action and communication plan for the demonstration and ask the organizers any questions you have about the plan before the demonstration.