Well it's a case where everyone's different and what one person might object to another will prefer. So you really can't win either way unless you are psychic and 100% accurate all the time. Personally I can't stand being "sweetie" and "hon" in the workplace. I find that highly inappropriate especially when it comes out of the mouth of someone 15yrs younger than me. But I choose to ignore it and just get on with job. I've come to realise that people don't mean to be patronising by using this, it's just their way of creating some level of familiarity and breaking down barriers. I'm happy to go with what makes my working life easier and more enjoyable.
But if it's really important to you then just politely say to the crew "you can call us...." and I'm sure they'll comply. It's really quite difficult to find the right balance as crew, I have my own system for addressing passengers that works most of the time. But occassionally I'll hit the wrong note, unavoidable unfortunately.
I have discovered that most people respond better to casual familiarity than not, it seems to be a very acceptable way to address people these days. And many of my mature passengers respond well to it.