Help, how long will my cake last?

[Vikingcake]

Help please, all advise welcome. I made the sponges 2 days before covering in buttercream and fondant icing. I've spent many hours making the decoration pieces (and a lot of money) for a mermaid theme cake for my daughters party tomorrow so the sponge will be 4 days old by then. Now, the venue has cancelled and postponed it until next week! Will it last until then now it's covered or have I got to start all over?

It might be a bit dry by then!
Do you think the decorations will last? You could store them and then just make another cake?

The icing will be fine but the cake might be a bit dry. I'd use it as the "blowing out candles/photograph" cake and buy one of those cheap supermarket party cakes (rectangle with smarties on it) to cut up and eat or put in party bags.