I'm doing my first buttercream wedding cake in December. I've worked with flowers on fondant cakes and they work well. I'm really concerned about the flowers on the front falling off, or tearing the cake. I use SMBC on my cakes if this helps. Her is a sample pic the bride sent me.

Glue them on to the butter cream using melted white chocolate and try to get as much surface to surface contact as possible for you heavy flowers. Also don't put your flowers on until a few hours before delivery so they don't get soft from the cooler.....and keep you cake cold while transporting.

Insert a small coffee straw into the cake, cut so it doesn't actually stick out of the cake. Then use a piping bag with some buttercream or white choco coating and fill the straw about half way or so. I use a tip 1. Then insert your flower (plastic or wire stem). The straw makes it all sturdy and keeps the wire from touching the cake...Or you can use those Wilton flower holders....

Thank you for your help!!!  I'm really excited for this cake.