It can be refrigerated. There is a risk of condensation if the cake comes from the cold into a warm room. If it should sweat, you can put a small fan on it. In any case, if you don't touch the surface it is usually fine.

The cake with filling should be cold when delivered and only be out in an airconditioned/cool room for a couple of hours. Once the cake starts to warm, the mousse can melt or deflate.