Hi JCarver2012,
Are you updating over the air through the device settings or are you updating using a computer? If you are updating over the air, then let's complete the steps listed here: If your iPhone or iPad won't update - Apple Support If those steps don't help, there's a section of the article that we wanted to draw your attention to in the event that the software itself is contributing to the behavior.
"Remove and download the update again
If you still can't install the latest version of iOS or iPadOS, try downloading the update again:
- Go to Settings > General > [Device name] Storage.
- Find the update in the list of apps.
- Tap the update, then tap Delete Update.
- Go to Settings > General > Software Update and download the latest update.
If you don't see the update in the list of apps or if the issue happens again, you need to update your device with your computer:
If you are updating using a computer, then it is possible that the software is being downloaded when the device is restarting. However, once the download has completed, then it should finish the update. These steps should help you to complete the installation of the latest iOS version onto your son's iPhone SE.
Best regards