First, you need to create a REST Api for your backend, here you have 50% of your solution done.
Then you must pick one approach based on your resources.
1- Hybrid app ( HTML5 inside a web container packaged for android / ios) and your web page.
2- Just your web page with responsive design.
3- Native app for ios / android and your web page.
1 - You can do this really fast if you already are a web dev, and you can get the functions of the phone on the mobile apps.
2- This will be easier to implement to you.
3- Native apps have better performance than hybrid apps and web apps.
Now, you have the resources for the first approach, the second one or the third approach?
All depends on that, but remember, if you go with a web or hybrid solution, take care of the performance of your code.