WGT doesn't/can't do anything at this time. All you can do is alert your members, put up a corrected replacement, and let the original flawed tourney expire.
Hopefully, maybe the ability to edit and delete tourneys will come along some day. It could be implemented, if we were able to give tourneys start times, instead of tournaments starting when we create them. There needs to be at least a small window of time between the creation of a tournament and the start of registration and play, to allow mistakes in the tourney setup to be corrected.