How do I manage my sons iPad on my Apple id

If he’s using your AppleID then he has the same access to all your data as you have. The AppleID defines the account for each Apple service (iCloud, FaceTime, iMessage, etc). Apple’s online system have no clue who is using the AppleID. The systems just know the AppleID. There is no privacy nor separation of data when people use the same AppleID.

An AppleID is a unique personal login ID. Everyone should have their own AppleID.

Coach_chet wrote:

they are both on my Apple id

Stop doing this immediately. Each person, regardless of age needs her/his own Apple ID.

The first thing to do is wipe his iPad.

What to do before you sell, give away, or trade in your iPhone, iPad, or iPod touch - Apple Support

Then:

Help your child set up an iPhone, iPad, or iPod touch - Apple Support