Playing Devil's Advocate here. How do I know you aren't a management mole? These things DO happen and I would hate to see an employee get canned over a cocktail if said "FF" was company security.

Having said that, i would have to had spent some time chatting you up as a FF before I would do this.

Let me tell you guys a true story and it may explain the caution.
Not too long ago, a CLT crew working to Europe noted that there were a few f/a's sitting in the back of the airplane who hadn't been in business class and asked them to come up to Envoy since there were plenty of seats open on that particular flight. Shocking I know. The upgraded F/A's were more than happy to come up and enjoy the service. Guess what? They wrote the crew up for upgrading them.

You never know people's reactions to kindness. It may not be what you expect it to be.

BUT....by all means send an A&B. Just leave out the part that could be perceived as theft.