I think I will go for it. The only reason I add the income info is that I've heard them in the past make snobby remarks about people who have more $$. I would really hope that me buying them lunch wouldn't look snobby in anyway, like I think I am above them and do more, sort of thing.
Take em to panera or a litte cafe. Just dont order a $100 bottle of wine at the most posh place in your city and I highly doubt they will think you are being a flashy snob.