I have a cake for a bridal shower to do and I wanted to do lace type of design to mimic the wedding dress. I thought about pipping melted candy melts on the cake... but I'm afraid that if I cool the cake in the fridge before covering it with fondant, the candy melts will fall off if the cake sweats a bit.

I've also thought about using royal icing, which I think might be better, but still, not 100%.

Please advise! Also, I don't like to buy any extra tools.

Thanks! 

go with royal, you will have more control and a finer finished product. 

You could also pipe buttercream onto the fondant. Candy melts would definitely be harder to manage since they'd keep cooling off.