If you want to make a relatively simple and straightforward change to your Will, you can use a codicil to do so without having to create a new Will.
Use this codicil to appoint a substitute guardian for your children. You might do this if one of your substitute guardians is unable to act as a guardian or if you didn't previously choose a substitute guardian. In all other respects, your Will remains the same.
Please note that you cannot use this codicil if you already have 5 or more codicils to your existing Will, as at this point we recommend that you make a new Will.