Add options and restrictions to products
1- Add the option to make mandatory that the user (guest) fills in information before they can add the product to their stay. Example: offer airport transfer but then make it mandatory for the user to input the time and airport of arrival.
2- Add conditions to products so that they can only be chosen if such conditions are met. Example: minimum of 4 people must book in order to book a ski lesson
I'd also add an option to set a limited number/availability to each product (as per places on a bus/sun loungers on the beach etc.)