For a public event, a release is often more about intended use and risk management than simply whether the event is public. Based on the answers, using photo-booth images as event coverage or “people having fun at our event” generally may not require a release, especially when participation is voluntary and obvious.

However, if images might be used in advertising, promotion, or commercial contexts, releases are more commonly expected. Many organizations handle this by clearly notifying attendees with signage that participation may result in photos being used, and offering an opt-out or removal on request.

For minors, if you want the strongest permission for broader promotional use, a parent or guardian signature is the safer approach. A sign alone may be used in practice, but it is less protective than written consent from a guardian.

In short: you may not strictly need releases for simple event-gallery use, but clear notice is wise; for promotional/commercial use—especially involving minors—written releases and parental consent are the safer route.