In all the weddings of the Greek royal house there have been representatives of the majority of royal houses. when it has been celebrated in London, have been authentic royal weddings, because all the real Houses have attended, this was so, with the Crown Prince Pavlos and the Princess Alexia. The wedding of Prince Nikolaos in Greece was conditioned by the place and the space, Spetses is very small, and a island,. There was representation of most of the royal houses, especially it was a princely representation, of the younger people. Queen Margaret and Queen Sofiam were in Greece and London .
If this is celebrated in London, will attend Queen Elizabeth, the agenda will not be a problem, it will be an event that will be on the agenda of the queen. Queen Margrethe will be present as well and Queen Sofía . Of the rest of real houses there will be representation of the majority, Norway, Sweden, The Netherlands, Yugoslavia, Bulgaria ....
But I see that Theodora is a very special woman, even she could wish for a more private wedding with her friends and family, in California.
I do not know what her decision will be, of course Greece is another option, it could be any island, although Spetses are more likely.