Booking Multiple Properties Together

Hi there,
I am constructing a property site which offers 6 properties to customers. They are able to book an individual property or multiple properties together depending on the number of the guests attending.

However when i set up the form for a specific calendar this allows customers to book and pay for one proerty. However how do they book and pay for multiple properties.

Is there a way to Add To Cart or something else so that they dont have to fill in a form for each and every property they want to book. That would be a complete faff to do and not a good user experience.

Any help/advice you can give to allow customers to book multiple properties together would be great.

The page I need help with: [log in to see the link]