How much your kids need to know will depend on a lot of things, including how old they are, how much disruption there will be, and each child’s temperament. Don’t overshare and unnecessarily stress them out, but don’t spring bad news out of the blue. Sometimes life hands you lemons and you just have to pucker. Moving is one of the most stressful things you can do in your life, try not to add to their anxiety. You can use this opportunity to teach your kids about making good choices from poor options, being responsible, and appreciating what you do have. Being poor isn’t the worst thing ever. Being homeless isn’t the worst thing in the world. There is always someone worse off than you.
When we drove across the country each child had two backpacks. One with clothes, and toiletries in a small bag you can carry into a Walmart or rest area bathroom inconspicuously. One bag for fun stuff, including handheld game systems, something to do when the power runs out on those systems, water, and snacks. We each had a sleeping bag as well.
If your kids have lots of gadgets you can get a car outlet splitter which extends the cords and lets you charge two things at once. You can get a USB charger for your car. You can also get headphone splitters so they can watch a movie quietly.
As we pack for this move we each have a bankers box that is for whatever we want to keep out. I can fit these boxes in the back of my car. I found that having something that looks different helps to avoid confusion and child panic when somebody tries to pack their sacred stuff in storage. You could use the fancy pants new duct tapes to make something stand out so it doesn’t get lost, too.