We recently started using a trailer, but mostly just car camp, such as next weekend in Mammoth.
We experimented with various sleeping config's, and have found that a good down or synth down sleeping bag and an REI 1.5" insulated pad for the kids and 2.5" for my wife and I. Reasonably compact and quite warm and comfortable. Pretty much exactly what was in the photos in the article. We cram our kitchen into a medium action packer, and the rest of the gear into another. We use milk crates for food stuffs, and one or two coolers for food and drinks. My wife precooks a lot of meals, and we pack them into the cooler in reverse order so everything stays cold longer. We have an ARB fridge, but we usually camp in bear country with food lockers, so we just use coolers.
Kids are incredibly adaptable, don't worry about them, but focus on Mom, keep her warm and happy, and everyone will have a good time.
I should add, with a smaller SUV like the Terra, you might consider getting a dog barrier behind the rear seat. This allows you to stack to the roofline, and things won't tumble down on the kids. Depending on the barrier, it can also provide additional tiedown points for securing your gear