The cancellation is due to low vis on the wrecksites. We just had a major hurricane pass up the coast and the long period swell takes out the vis. Sometimes it clears in a few days other times it takes a week or so. They are doing the right thing with cancelling this weekend and there will be steady improvement over time as the sand and sediments falls out of the water. Next week the vis may be just a bit fuzzy but the diving should be good, plus lots of new stuff will be exposed and who knows just what you might see. Check with Olympus before your trip and they will tell you like it is, they are a good operator.
The movement of the wrecks is common after such an event, especially the artifical reef sites. They are not yet as broken down and embedded into the bottom as the older wreck sites, so they can move around a little. Not a real issue for a dive boat to relocte them as they don't go far. It is just like the old days prior to GPS - you get near the spot and start a sonar search. The older sites just get slightly rearranged and change a bit in appearance.
