I'm unable to add my 9 year to family sharing as I have to put in credit card details , I don't have one . I only use a debit card.

Apple requires a credit card to be entered for child accounts : Family Sharing and Apple IDs for kids :

To comply with child online privacy protection laws, you will use the CVV or security code from a valid credit card as part of providing your parental consent. If the card on file is a debit card or another payment method, you’ll be asked to provide a credit card before you can continue. After you create the child's Apple ID, you can change your payment method back to a debit card.

So as it stands you won't be able to without a credit card. You can try leaving feedback for Apple, but if it's there for online privacy laws then it's presumably unlikely to change : http://www.apple.com/feedback/

My bank issued Visa debit card can be used as a credit card to make purchases, and includes a CVV number on the back. Apple still won't let me use this as a valid card to create a child account.

It has to be a proper credit card, not a debit card.

I have never heard about not being able to use a debit card with the visa/MasterCard logo for payment method and to set up the account or child account. I have been able to use my debit card with MasterCard logo with all. I have had no problems what so ever. I know others that also do the same using debit cards with Visa/Mastet add logo and again they never had an issue doing this either. I have never heard of this before And I have never heard of anyone having issues with their debit cards jot being accepted for it. Come on Apple. With technology today and how far advanced Apple is and there is this minor issue that shouldn't even be a problem for anyone.

We are fellow users here on these forums, not Apple.

Read what I pasted in my first reply. Debit cards can be issued to people below age, for child accounts you are taking responsibility for their purchases and have to be of an age to have a credit card to do so.