We have the same policy (absolutely no open flames anywhere), and with all of the flameless candle options out there now, it really hasn't been an issue for us at all. 

Has pushback been happening before or after a contract is signed? It should clearly be stated in the contract, and explained during a walk-through. If they don't like it they can choose to go elsewhere. And honestly, if having an open flame is a deal breaker, I'm not sure I'd want to deal with that particular bridal party! ;)