My sister had one, although she was in brisbane, so can't help with Melbourne side of things.
But she had 3 tiers - chocolate, peanut butter and some fruit flavoured layer.
It'll be fine, most cakes have to stay in the fridge anyway so the reception should be able to have a spot for you. And it won't melt, places that specialise in the cakes make them so they know they have to stand up to long periods not in the fridge. I recommend that you just go to a place that specialises in it and talk to them about it and try some flavours