Would you blow them up the evening before or on the day?
and what about the cake...left out the night before or on the day?
Unless you have foil ones, helium balloons don't have a very long life span and should be inflated as close to the time as possible. If you blow them up the night before they'll probably have sunk and started to shrivel I'm afraid - currently trying to work my way round this so I can't give you any practical advice.
As for the cake, depends where you're talking about putting it - if your venue has other things going on, I'd ask them to keep it tucked out of the way for you.
Posted this on another thread, but...
I found this thing called hi float. If you use that on balloons you can blow them up the day before and they last ~3 days. That's what we'll do.
Not sure baout the cake. We'llmake it the day before. Probably it's okay out overnight, but I might prefer to set it up but keep it covered and have somebody whip off the cover before the reception.