Unable to factory reset our son's iPad in order to change personal details.

Our autistic son's care home has returned his iPad, because he kept messing up the settings and I've tried three times to factory reset in order to change personal details, but after the reset completes and I start to set up the iPad, it still asks me for our son's passcode and nobody has that code. We have his e-mail that's associated with the code, but not the actual code and the problem is that his care home doesn't have a record of that code either. I have my own Apple ID and email, but the demand during the setup process is for our son's email and passcode, because it was his machine. The snag with his care home is that they have a huge staff turnover, so whoever set up his Apple iPad has probably left the care home. Please could someone advise how to resolve this factory reset issue.

Many thanks for your kind assistance,