What if one participant doesn't speak English?

From time to time, I help Spanish-speaking couples fill out their divorce settlement forms, but only one person speaks English and translates for the other. These are simple, quick sessions, and it seems both individuals just want to divorce without any complications. There is no negotiation, they already have an agreement on what they want. I always advise that they retain a translator, but I do wonder about the ethical and power dimensions involved when only one person speaks English and translates it to the other person (and it has always been the male partner who speaks English).