I have 2 children at the same Club, can I use the same email address for the accounts? 

Yes.

-If your Club have paid for you to have an account then you will receive a welcome email to sign up. If you have been registered for 2 children by the club, you will be able to set up both by following one welcome email. If you don't use the link in the Welcome email, log in to the Parent account; you will have 2 accounts both with random capital letters, you will need to "edit child" for both of those accounts and set them up with different usernames and passwords.

-If you join TopTekkers as an individual user and you have 2 children then you can have both child accounts linked to one email address if you choose to. Just go ahead and "add child" in your Parent account.