It doesn't matter, but you obviously have to pick one. We is more common than wij. But if the word is stressed, wij is the only option.
In translations, normally both should be accepted. In dictation exercises only the one that is actually spoken. Theoretically. In practice the fast voice pronounces both as we, and you must check with the slow voice.
The problem has nothing to do with Dutch. "We do nothing" would be a correct translation if it were the normal way to put this in English, but it isn't. If it is used at all, it carries a special emphasis that is not at all implied by the Dutch sentence, though of course nobody prevents you from stressing niets a lot.
Personally I think it should be accepted, but it also makes some sense to reject it.