Automation of web browser based application

Need some guidance.

Need to automate a web browser based application.
ie a website.
On Android, IOS mobiles, windows and iOS laptops/ desktops, iPads/tablets.
Need a complete cross device, cross browser testing setup.

Can Appium be used for the whole setup?
We have selenium for browsers and Appium for mobiles. How much code will be reusable?
Any suggestions how to achieve it please.

Thank you.