Decorating little shaped cakes (from silicone moulds)

It's DS's fifth birthday on Sunday, and I have one of those silicone cake moulds, with about eight little car shapes on it. I also have a butterfly one for DD, but that will be for another time! How do you decorate these sometimes quite intricately shaped little cakes? It's way too big for a chocolate mould, so let's not go there. I was thinking rolled fondant, but that will be tricky, and I just had an idea now as I was typing, what about "poured" fondant? Or a thin royal icing? And then details could be painted on.

Thoughts? Most appreciated.

Ps, happy new year everyone! :)

I have no idea how they expect you to ice and decorate that! I'd avoid doing it on the cake, I'd cut those bits off and ice it smooth like a regular cake. Then press fondant into those shapes, or put chocolate in them, and just place them on top.

Never heard of poured fondant before, so no advice on that one!

I'd use butter cream and pipe little stars all over the cakes. Sorry, I don't know the correct term for it.

I had terrible trouble decorating the dinosaur shaped moulds I got for DS' birthday...tried a thin icing but it just ended up drizzling off and pooling in the hollows iykwim? Thicker buttercream icing was the same. DS didn't care but they looked like blobs of yuk to me....couldn't tell what they were at all.

Bit late, but I add food colouring to a small amount of cake mix, put it in the correct area, then normal cake mix on top. Sure, it isn't icing but cake has enough sugar in already for me.

Butter cream all over then cut fondant icing to shape and place on top.