Good luck to you - I have done this on the past several cruises and I love coming back to my room and seeing the flowers! Ironically, we sailed out of Brooklyn last September and I did NOT get flowers because it was pouring rain and we walked from our Financial District hotel to the ferry and then to the embarkation point....didn't need the hassle. So, I dragged my vase all the way from Canada for nothing. Yes, I pack my $2 Dollarama vase with me (stuff it full of clothes) in case I can't get a vase on board and also that way I don't have to inconvenience anyone.
I have my fingers crossed for you that it all works out.