Just remember they probably have a camp store and of course there will always be a WALMART and a LOWES close by.
Some folks like to camp out in the back yard a couple of times to really figure what what you might need...
Just go enjoy your self. You will see what others bring along and decide from that what you all want to bring with you.
I end up going overboard as I have the room and like to cover all of the bases called having PLAN Bs. For us this is great but for others its probably a waste of precious storage space...
The dire necessities are being able to hook-up to utilities if the camp site has that available. Water hose and cable TV connections are high on the list.
Most camp sites have pedestals for 30AMP and 20AMP connections - some have 50AMP connections.
If you are camping off the power grid you will find out real quick just one battery will be a bummer. Especially if you have to run your propane furnace any.
Your new trailer will have all of the modern day appliances and you will want to run them. Its not like the old camping days where you can survive with flashlights and candles. You can still do that but there you sit looking at the modern appliances sitting there idle.
You can go overboard rather fast here haha...
Roy Ken