Great advice so far, been camping and offroading for years in our Wrangler.
Sunscreen, hats, lip balm you can get blasted by windburn and sunburn after a long day of Jeeping. Bug spray, get it use it often and before any issues, better to prevent than even think of dealing with any. Get a good first aid kit and make sure you add aspirin, other painkillers, cortisone cream etc.
^^^^^^ The above should be in your Jeep forever, when traveling or offroading add tree strap, tow strap (no hooks is best) and a Hi-Lift.
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Be aware if you are not familiar a Hi-Lift is a fantastic tool that can be used for clamping, lifting, winching as a come along but it is a dangerous tool that needs to be used carefully and with full knowledge of how it works or may not work.
No matter what tent you get, set it up, seal the seams again and waterproof again. I have done this with every cheap and expensive tent I have ever bought, this along with good site choices and never letting a ground cloth stick out from under any edge of the tent has resulted in never having any major rain or water issue.
Couple of decent (can be inexpensive) head lamps (I would have one for everyone including the young ones, makes em easy to spot) are small easy to use and functional.
Two to three days a decent cooler should take care of your needs. i would recommend ice and blue packs etc., for the cooler. If you can get some block ice even better it will last longer. I also always freeze a few water bottles to use for ice in the cooler (sometimes a lot) and after a day or so they can be used for drinking. If you are going to carry drinks or snacks or anything else that you will be going into the cooler for over and over bring two smaller ones. Keep meat, milk anything you are worried about in one cooler that you do not open often.
In your situation, hitch rack if possible (depends on how much and type of offroading prior to campsite) in the future a small trailer than can be towed offroad is a fantastic addition. You might want to look at a roof rack moving forward as well, makes taking the top down more problematic but can add tons of storage.
Having a usable bathroom is important for girls, I use
Portable toilet no water the bags are land fillable and it works great with a small bathroom or shower stall.
Two gallons per day is minimum IMO, carry more if you can. The first trip is a great time to get a handle on how much of each consumable you will use.
If you have nothing else a small solar shower bag warmed in the sun can be one of the most fantastic things ever after a day or two camping. For the future plan on getting a Zodi shower (portable water heaters that use propane or a camp stove) or do what I did and add a hot shower to your Jeep using the coolant heat and a 12V pump.
Like above posters keeping every one dry, warm comfortable is imperative for happiness and future trips.
Bring some cards, books etc. in case there is bad weather, want to have options for entertainment.
Ask more questions we should be able to come up with answers.