Shepp sounds good -- at least he was in fine form when I saw him a couple of years ago. Wonder if they'll bring out any of the old Shepp-Burrell chestnuts like "Blues for Donald Duck," "Hipnosis," and "Sonny's Back?" I suppose those are all Grachan tunes, right?
I saw Keir in duo with Shayna Dulberger once, and that was quite strong, so I think you're in for a treat.