Excuse Me!?!
Perhaps the OP's company pays for fiances to go on business trips, but I certainly have not worked for a company with such a policy.
I believe that it's entirely appropriate to bring up ethics, if the OP is proposing something that could be interpreted as being unethical at best, illegal at worst. He may not realize that he could be terminated for violating the company's travel policy. I would check the policy before doing something like this.