Setting up together is a big part of the fun. The more you have stuck together ahead of time the faster it will go. If you aren't able to stick details on ahead of time then be sure to set up the scene before hand and then bag the parts and figures in groups and keep them with the related structures or scenery. Knowing what you are doing and having all the parts together ready to go will be much faster than having to hunt through boxes for stuff. Good luck it sounds like a fun day.