I haven't been in that situation myself, but have seen my dad do it several times (my parents like moving across the country – if we're in the midwest, next move is to the west coast; if we're in the south, then it's time to move to New England, that sort of thing 😛 ), and he always made sure that he was wearing his interview suit by the time he was seen, which usually meant when he left the airport. I would be hesitant to pack it in carry-on luggage for fear that it would be all wrinkled on arrival. As much as suits are uncomfortable, I'd try to suck it up and wear it for the trip, too. I would definitely wear it for the luncheon. Of course be careful if you're eating spaghetti or sloppy joes 😉 but I would wear it. Always better to be over-dressed than under-dressed.
As for the conversation, again, my experiences with this have been more post-job-offer/acceptance than during an interview, but I would anticipate neutral, only-vaguely-job-related chit-chat. This is probably the time that they're evaluating your ability to interact with the team rather than your technical qualifications. If they asked you about GLs or audit procedures over lunch, I would be highly surprised…but if they asked you what your hobbies were, I wouldn't be surprised. They probably won't ask you if you're married, have kids, your age, etc., since those could be seen as discriminatory practices, so I'd expect quite neutral topics that can help them gain insight into your ability to interact with a team, but remain friendly and non-discriminatory.
…and if it was me, I'd be lucky to eat much and probably wouldn't say much. I can make a great impression in a “real” interview, but things that are half-business, half-friendly have always been a struggle for me! Like, when my dad ran a business out of our house and employed some guys from our church who I knew, I found it so awkward to make small talk when I knew they were at work, not at a social gathering…but at church on Sunday I could talk their heads off. So, I'm glad it's you going to this luncheon interview and not me. 🙂 But I also think that luncheon things can be a great opportunity to make people like you even before they know if you can do the job, so it's a good way to up your chances of getting the job. Let's face it – anyone can do accounting. It might come easier to some than to others, but anyone can do it. The only thing that the other candidates can't do is be you, and a luncheon provides a more relaxed environment in which to show who you are and win them over.
Good luck!! 🙂
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