@dd100471
If your son is playing on a guest account that progress is saved to the device and not the cloud servers, so if the game is uninstalled the progress will be lost. Since the data isn't saved to the cloud servers via Google/Apple accounts, it cannot be transferred to another device.
What I do recommend though is having your son write down his NBA Live User ID (located under Settings) that can be helpful for account recovery.
How to find the NBA Live User ID: https://help.ea.com/en-us/help/nba-live/nba-mobile/find-your-nba-live-mobile-user-id/
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