Yes. Issue the player a generic DCI card. When you enroll a player in an event in WER, enter the number of the DCI card along with their first and last name. Then hand the card to the player and encourage him or her to follow the link on the card to create a Wizards Account at a later time.
Once a player creates a Wizards Account, they can claim the DCI number as their own. The first time a player claims a generic DCI card, they will be awarded 5 lifetime Planeswalker Points.