My mum and dad both want LPAs — do we need separate documents for each of them?

Yes. An LPA is personal to one donor. Your mum needs her own Property and Financial Affairs LPA and her own Health and Welfare LPA. Your dad needs his own of each. So four documents in total, with four OPG fees (£368 unless they qualify for fee remission). When couples do this together, we can usually do the same-day consultation as one joint call to save time, and the documents are drafted in parallel. It's worth doing both partners at once — the discount in time and effort is real.