Software for managing a hotel with campsite wanted

We have a campsite with approx. 50 pitches, a hotel with 33 rooms, 4 vacation apartments, 4 cyclists' cabins and a marina. As support for our current software has been discontinued and the solution no longer meets our requirements, we are looking for new software.

Requirements for the software:

• You have to be able to reserve, pre-book and cancel bookings.
• Billing, including VAT, should be as uncomplicated as possible.
• An integrated cash book, preferably not manipulable, clear and easy to understand.
• A Datev interface is mandatory for monthly cash book entry and transfer to the tax office.
• If possible, we would like to introduce an online booking system that automatically records bookings via the Internet. (not absolutely necessary)

The use of the software is planned for 2 workstations.