cxl; probably doesn't qualify as a cancellation, since it was never much more than a whisper. LIA quotes Tom Zito: "The Dead would like to liven up the Washington area with a free concert on Aug. 22, but are having a tough time finding a place to do it." The "Caravan of Love" tour is heading east "enroute to an Aug. 25 appearance at the Isle of Wight Music Festival."
This tour did in fact happen, and was filmed for the movie, but the GD backed out at the last minute. Alembic however was still under contract to do sound, so mixers Bob Matthews and Betty Cantor and the sound crew went off with the Caravan.