From the contexts in which I have heard it used, and also according to jisho.org, the word 連中{れんちゅう} appears to be a fairly informal word, on par with the use of the word "lot" in British English as a collective noun ("you lot"). However, it is unclear to me exactly what situations it would be okay to use in, and exactly how impolite it is. Furthermore, it doesn't seem like there is any one word that can be used to replace it in situations where it is too impolite.
The circumstance I am thinking about is one in which a close group of friends is talking to one of their member's older brother, in casual but polite setting; the older brother refers to them collectively, remarking jocularly on how difficult it is to hold a conversation with them because of their inclination to 突っ込む.
「君たちはとんでもない連中に違いないです」= "You guys really are a formidable/difficult bunch"
In this context, would 連中 be too strong/impolite a word, or is it appropriate for such a situation? If the former, is there a better way of saying this?
I know that the translation is not 100%, but I am translating from my own words, so the intent is more important than literal accuracy.