We are having dinner at CG with our intimate wedding party and asked our coordinator about private rooms, etc, as my future father-in-law was inquiring. CG does have private rooms you can rent with a food and drink minimum (different for every room). I want to say the lowest minimum is around $2,000 for a small room. Your EM should be able to supply you with all the information.
If you are having your reception during the day before CA grill opens, all you need to meet is the normal FTW mins, instead of the private room mins. it is definitely an option and a very cool location!