Pokémon.com/Website Sections/Pokémon Trainer Club/Child Accounts

Adult parents may create and manage separate accounts for each of their children in the User profile section, which is accessible through the adult's "User profile". While The Pokémon Company International strives to be child friendly, parents may further restrict access to certain website and in-game Pokémon Trading Card Game Online features. For examples, some in-game features such as "Public Chat" and "Private Messaging" in the Pokémon Trading Card Game Online are always inaccessible with a child account, while other in-game features may be further restricted by the adult parent such as "Friend Chat", "Game Chat", "Shopping", and "Trading".

For step-by-step instructions with screen shots to walk parents through the setup process see – How do I set up my child's Pokémon Trainer Club account? on the official support website.