Just got three e-mails (one for me, one for my wife, and one for my daughter). My wife (after registering) will receive triple miles for her dines. My daughter and I will get double.

The double/triple only applies to specific restaurants that 'invited' me. Here is one of the responses after registering.

Thank you for registering for the Triple Feature Bonus. You are now eligible to earn triple rewards on Mondays, Tuesdays, and Wednesdays from 5/30/11 through 6/30/11 when you dine at one of the participating restaurants listed in the email inviting you to register for the bonus.

Not sure how they decided who is targeted for double and who is targeted for triple as we all are currently getting 5 miles per $. The only difference is my wife has met her 12 dines for next year whereas my daughter and I are each a few dines away.