I think “kak” would be better translated as “poo”. Parents will routinely talk to their kids about “kak”, similar to the way US parents will use the word “poo”. The word “shit” generally has a much stronger meaning (and is therefore often obscured, as “s..t” or something similar.
I think "kak" still would be translated better as "shit", you wouldn't curse with "POO!". But in Dutch you can curse with "KAK!", just as 'SH*T!' in English.