My son loves Tish Boyle's caramel espresso bc (french bc based) and requested it for his 16th birthday this Saturday. I am covering the cake in fondant, and want to avoid refrigerating it (afraid of condensation, bubbles, etc).

I thought about using regular buttercream or even Bettercreme, but am afraid that adding caramel to either one will make it too sweet. Can anyone help, please?