A "dinner event" is a business, not a consumer, transaction and it is presumably governed by a written contract which lays out the terms, if any, under which it may be cancelled. Hilton has made a decision to deal leniently with consumers. But, when it comes to a business transaction, there is no argument for Hilton to accept all of the risk.

What does the contract say? Without that information, nobody here can provide you with any information.