Adding money to my sons family account position

Yes, you can pay the last part by card.

Where would I be able to add that last amount needed . The Adding money section only allows multiples of £10 ?

I am not sure what to do as in my account I have my son twice as a family member with different email addresses I was for tracking him on his phone the other was for xbox. I have added money to the account that is for the microsoft family feature of keeping a child safe.

Is your son account added to your Family group?

I set up the new Xbox with the same account as the old one. Made it the Home console. Then added my son's Microsoft account as a family member.