I got confused when you said the CO coldcalls. Was there a raise preflop? I will assume there was not. Since the pot is only 4 small bets, you should bet since a bet will protect your hand from any gutshot/5 outer draw. I know the BTN is aggressive, and if the pot was bigger or it was 6 handed or more going for the checkraise would be the better play given your read. But in your situation in a 4sb pot with just 3 opponents, youll get more value out of a Bet/3Bet line than going for the checkraise.