I have seen bears peel open some sizable sedans for the snacks inside. If they are determined to devour your cooler, then by all means, let them have it. A cooler is much cheaper to replace than a Chrysler. Making lots of noise will usually shoo them away, but don't press the issue. Bears are bigger and stronger than you and they are quite secure in that knowledge.
All reenactment organizations have safety rules.
Usually, only battlefield combatants are required to read and be tested on these rules. All civilians, young and old, should read these rules and know them by heart . Know the standard safety distances and do not violate them. Combatants are very careful, but you are responsible for your own safety - do not depend on them to watch out for you. Never handle or touch another reenactor's weapon without their express permission and presence.