In settings I can’t access Apple ID on my kids ipad

I can't guarantee a fix, but see:

Why is my Apple ID setting greyed out on iPad?  https://discussions.apple.com/thread/8355468.

A post in this thread says:  "I just found the reason for my Apple ID Settings being greyed out. When I disabled Restrictions, my Settings became enabled and I was asked to update Apple ID Settings. S O L V E D...

Apple ID banner grayed out https://discussions.apple.com/thread/8611970. This one reports a solution also having to do with restrictions.

 My Apple ID is Greyed Out in Settings, Fix https://macreports.com/my-apple-id-is-greyed-out-in-settings-fix/

This occurs “most likely … because of a problem that happened when upgrading the iOS or when you change your Apple ID and password.”

So, you might use What to do after you change your Apple ID or password https://support.apple.com/en-us/HT204071

To get Apple Support for help with your problem, see:

Apple ID Support https://support.apple.com/apple-id

Apple Support Twitter  https://twitter.com/AppleSupport There might be an hour or so wait.

Apple ID account security for country-specific and region-specific help https://support.apple.com/en-us/HT204169

Get Support: We’re here to help https://getsupport.apple.com/. Go through the options to find the best support option for you.

Have you checked Settings/Screen Time for any restrictions?

Try a restart.

Restart your iPhone, iPad, or iPod touch         

Try a forced restart.

Reset Device.     

If necessary

Hard reset.        

If there are restrictions in Screen Time that are preventing access, you will need to restore the device to factory settings. Do not restore from a backup made when the Screen Time code was active.

If there aren't any Screen Time restrictions, do a backup and try a factory reset. Then restore from your backup.

Restore to Factory setting.      

Backup - Restore your device from an iCloud or iTunes backup.