I did London for the first time last year. I stayed by Canary Wharf. Ideal for the expo and getting to the start, both with the DLR. Plus the race goes right past, so family can stay in hotel and pop down to see you. You can arrange an exact point as the barriers and mile markers go up the night before. The family can then jump the tube (jubilee line) towards the finish for a meet up. Tube back to hotel afterwards. Lots of stairs on the way back on the tube however.
Edited: 21/11/2012 at 19:05