Django is fine, if a little heavy but it will provide a good restful API.
For the app - I'd really recommend dipping into Flutter. The language is simple, tooling is great and you can get up and building rapidly.
I'm keen to try out Flutter as I've heard good things, but I'm weary of delving into an entirely new language for this project if the languages I know already offer a viable (and popular) mobile app dev stack. Unless it really makes state handling on the UI mega simple, which is my biggest problem with the JS library/framework solutions I've worked with before.
Try out both and check them out. The dev experience on Flutter is in my opinion far superior to React Native. It just works whereas with RN I spent so much time getting things to work correctly, even with Expo. I am not sure why it's so terrible given that create-react-app "just works" almost as well as Flutter.