Google maps in mobile app/web without billed

Hi. We are developing a mobile app connected to a web server. It is a freeware app for animal rescuers. We expect thousands of users to use the application and it appears that google charges $ 4 per 1000 loads for the location details beyond its free usage of $ 200. We can not afford that since each mission will involved marking 2 locations or more. We are picking up lat/long from the mobile phone however to convert it to an address we need a solution that doesn't cost us for each transaction/address road. We also need to calculate the path traveled by the rescuer. We are using react-native framework for the development. We need help from an experienced mobile app developer who has overcome this challenge.