A few days ago I saw a National Park Ranger present in this setting below: 200+ getting and eating their lunch, continuing their conversation, while the ranger used a microphone to top the noise level of the crowd, reading from a piece of paper. A bit like Alaska salmon swimming up river, or the jazz band that is ignored in the background of a cocktail party.
A better approach: shorten the talk to focus it solely on the memorable facts: how big this National Park is, how powerful the 1964 earthquake/tsunami was and what permanent changes it made to the landscape. The philosophy behind the National Parks is less interesting for the hungry crowd.
Photo source: alaska.org