I have one advise for you, don't assume that because a candidate is more senior than you, he or she should at least know what you know. Try instead to learn so

I have one advise for you, don't assume that because a candidate is more senior than you, he or she should at least know what you know. Try instead to learn something interesting from the candidate. At the end of your lunch, if you learned something that could help you in your day to day tasks, or in general, maybe it's a thumbs up from your perspective. Let the rest of the team figure the rest out.