Wow, Julie, that’s just a fabulous bake-off adventure and you took us along for the ride! I think your cake looks fabulous - the combo you used sounds delicious - did you put chocolate in the cake in place of the coffee? The glaze is a wonder of wonders.
I too think your rose (and your daughter’s) looks magnificent and it’s great that they keep so you will be able to use it later. As for the chocolate leaves, I have never made them but thanks for sharing your experience. It seems like rose leaves or holly leaves would work as they are thick and sturdy. About the leaves being dull, tempered chocolate will take up the sheen of the material on which it is dried. So, the industry uses shiny moulds and acetate to get that lovely glossy finish. If you want a dull finish, just put your chocolate on parchment paper - or the back of a raspberry leaf!
Thanks for being so detailed in your reporting.