Is it practical or doable that I ask users of the app to provide their own API key, and tell them without that, the app wouldn't work?
I know this, if possible, will force them to open a Google dev account
Without knowing the type of app you are talking about, I think it is doable if you can provide a video tutorial on how they can obtain their own API, otherwise it could limit the users who would use your app to only more advanced users.