How do I reset my son's iPad password without access to the old one?

Hello. I have just purchased my son his new iPad for Christmas. His old one sat beside it on set up. Transferred everything over and looked great. Each app was a cloud and when I clicked on anything it asked for his password. I have no clue what I set this as so I chose “forgot password”. I went through a security confirmation which is my mobile number. I then got a code. It then asked for his email address where another code was sent. It then said we would hear in 24 hours time as they couldn’t match everything. Which is weird considering I entered the codes I received. So I done it again. I got this ismda or something to reset his password but just asked for his old one. I am at my end with it. He didn’t have a passcode as he’s 5. So I set one. Still no access to reset a password. Now I cannot remove the passcode without the password. If anyone can help me that would be great. To top it off the charger broke. He is also down as a family member linked with my Apple ID but no where can I find where to do it on my phone either.

[Re-Titled by Moderator]

Original Title: Password help