Great Race Reward Credits....When?

Son received his as well - it will be fun to use them all!!

Has anyone verified whether the Great Race bonus points' expiration date will be extended each time one puts in more points, just like regular bonus points---or will these points all expire in May 2012? Do I need to spend them all ASAP, or can I slowly enjoy them?

Good question, but there seems to be No difference in added RC points.
Since they were just Added to your other RC's, I'm expecting them to be treated the same.

Do I qualify for Diamond status bcause I got more than 11000 a year?

You do if you earned 11000 Tier points. These are bonus points and have no bearing on status.