We brought a bigger tent, plenty of rainy weather gear and had a reservation for a campsite along the river. We enjoyed ourselves despite the cold wet rainy day. We visited vendor's tents, looking at lots of cool stuff for the 4Runner and gathering lots of valuable intel.
We came to the agreement that we would car camp on our big cross country trip with a traditional tent (a 4-man size at least) and not invest in anything too extravagant until we were certain we needed it. Campers are nice but we weren't sure we needed that comfort level versus saving some $$ and taking more or longer trips.
Now we will spend the next few months doing lots of online research and watching many many many You Tube videos about overloading adventures.