This will remove somebody from TWRFC in GMS, it will not remove them from either the age-group mailing list, or from mailchimp – the parent can remove themselves from those using the links in the signature of every mail sent.
Go to the people screen, and search for the child you wish to remove.
People can only be removed from the club if they are not registered as players; if the person is registered (i.e. has a ‘Yes’ in the Player column) you will need to de-register them first – this is covered in THIS GUIDE
If the player is not registered you can remove them by selecting them, and from the ‘More’ menu, select ‘Remove from Club’
Finally you will be prompted with a confirmation screen where you can make notes as to why you are removing somebody. If they show as having active membership please exercise caution and only remove them if you are sure they have left.