I'm trying to change my password to log on to my grandson iPad

Passcode or Apple ID password?

For the Apple ID password, if you know the current password, try the links below.

 Apple ID Password Change.      

 What to do after you change your Apple ID or password - Apple Support     I suggest doing this before you change your Apple ID or password.

If you forgot the Apple ID password, enter the Apple (iCloud) ID and click Forgot Password.

Apple ID - Manage            

Apple ID – Forgot Password            

For a passcode change.

Passcode - If you forgot the passcode for your iPad or your device is disabled.