Need to create a web based booking management system for internal use

We are a small tour operator based in Denmark with 3 people, we sell packaged tourist product to B2B customers.
The packaged tour is based on the price data we have prepared (key in) from various contracts with suppliers. We would like to create a web based booking management system to compile the packages and generate document such as vouchers, list of suppliers, or automated emails etc.
There are some ready made solution on the market to license, but we would like to be able to have the full ownership of the solution and not dependent on others.