D.K.
Maybe these will at least get the creative juices flowing.
Refrigerate the flowers until right before the cake is put on display. And cut off all but about 3 inches of stem and just stick them into the cake. I recommend roses (some open, some still buds and some in between) if one of the colors is pink, and maybe some real silver ribbon (the kind for making elaborate gift bows that has wire in the sides so it will keep it's shape) in a cascade down from the top. Just put two together but perpendicular and punch a hole through where they meet and stick a straw in it to keep it in place as you stage the ribbons down the rest of the cake. Right before serving, stick the flowers through the hole and anywhere else you want them. it sounds kinda pretty without being tons of extra work.