Writing rates for the periods you sell
Write your rates for the periods you genuinely sell, and be honest about seasons rather than inventing them. Count your extras — the actual number of helmets in the actual sizes — because the value here comes from the number being right. Decide your deposit rule and your cancellation rule and write both in the words you would say to a customer. Decide who is allowed to change a price on a confirmed booking, because that is the permission that matters most. Then take five recent bookings and check that the figures on them are what the customers were actually told.
Not a payment processor or accounting tool
It records the commercial agreement. Collecting on it is your business.