An option picked up from Alton Brown which works well for us with the very thick cut steaks we generally use (we get them cut to order at Publix when porterhouse, etc. are on sale, and freeze) is to grill the steaks, then cut off the bone into several ounce pieces, and allow guests to select their pieces, from a passed plate or buffet.
We cook a bit more than expected will be eaten, and have found this worked well among our friends - where some may eat more than a single steak, and others are not likely to eat a full steak. Also, it is evident to what degree each piece is cooked.