🔥 Firebase tech stack predicament for invitation only MVP

I am in the predicament (see my tech stack is below) of picking what to use in firebase (web or phone app) but in my case product requires for the user the phone camera, I have render the app in my phone and it works. I am actually planing to do a invitation only MVP launch to get user feedback, can the users access the web app easily? is it going to be hard to create the app for ios and android?