I too keep reading that it will be shorter and more low key than the last Coronation. However, this past week has shown that there is still an appetite for royal ritual and ceremony in Britain. I would think that King Charles would not want to dispense with the Crown of St. Edward, given his love of tradition. I think they will have to modify the Imperial State Crown. Queen Camilla could be crowned with the same crown that was made for Queen Elizabeth for the 1937 Coronation.
Given that she has no constitutional role she doesn't need to be crowned at all. After all, her late father-in-law was not acknowledged in any way when his wife was crowned. If the new king is serious about modernising this somewhat outdated ritual, here is where he could start (although given his blind devotion to his wife he probably won't).
http://europeanroyalhistory.wordpress.com/523