If your website is configured correctly it will act as both a Sales tool that will bring you new business and a Fulfulment tool that will process your reservations and take care of much of the admin.
What is important here is to capture the Sale first … and then work on the Fulfilment. Rather than have one long booking form asking for names of each guest, addresses, passport numbers, dates of birth etc have a simple form instead in front of the checkout, and ask all that detailed other stuff later.
Requiring your guest to provide information that they might not have to hand is stopping them from making a booking