Re: Credit Card chargebacks. FYI, it will affect your credit rating. Secondly, I am not sure of the lease agreement but I highly doubt it would have been invalidated by the lack of beach chairs since that is a 3rd party responsibility so even if a chargeback is granted (which means nothing legally) the guest still has legal obligations under the short term lease agreement. Best course of action is to reasonably negotiate between both parties.
Risking getting dinged on a credit report for a such small amount may not be worth it in the grand scheme of things.