If by "non melt" cream you mean non dairy whipped cream, fondant and gumpaste will melt and slide right off of it. It is to "wet" and the fondant or gumpaste will dissolve.
I use non dairy whipped cream on 100% of my cakes...
I use them all the time with much sucess. I get air bubbles because I frost with non dairy whipped cream which is really "wet" compared to fondant or buttercream. With air bubbles. I just make a tiny hole in the bubble with a pin and...
I have done this but not with butterflies. I only frost with whipped icing so I have had to experiment with fondant accents also. My advice would be to dip the butterflies in melted chocolate in the same color as the cake. Just...
I love those candles. But couldn't you make a little ball of fondant, flatten it a bit and insert a smooth candle into it? I think in a pinch, that would work.