You need to sort out something very important.
Boy do I hope that you started this order with a written contract.
You will be delivering a tall cake a day ahead of a party? Transport the topper separately. Take a carpenters level and some scaps of wood with you, to test the table before the cake is set up.
You need to make very sure that you take pictures of the cake after you have finished setting it up.
You also need the customer to sign a release form stating that your cake was in perfect condition at the date/time that was agreed upon...because there are many accidents that can happen when you leave a cake somewhere for a day.
Many of us have had a bad experience with a cake delivered a day ahead. The venue will move the cake--usually the wrong way--and cause damage. And then the cake maker gets this nasty demand for a full refund of the $$$.