Some way to wipe-down / clean before bedtime, especially if sunscreen/bug spray is to be used. Like Baby wipes or a wash rag and watered-down alcohol.
Some kind of a large plastic bowl / small basin for washing dishes, hands, kids, etc.. For car camping, I always have 2 that nestle within each other...one for washing and the other for rinsing.
Toilet paper, baby wipes and a small shovel for cat hole toilet.
First-time women and kid campers feel strange about poppin' a squat in the woods to shit, so some kind of a shitter seat may be worth it. I used one of these LINK
(minus the bag) for years until the wife and kids got used to squatting over a cat hole.
A whistle for the girl to always keep around her neck. I put a whistle on every kid so they can blow it if they get lost or need help when out of sight or playing in the woods.
I also ensure kids are wearing a bright colored shirt (preferably bright red or orange) for a multitude of reasons.
Flashlights...big fun at night (and practical).
Some kind of treat that they're not normally allowed to have at home, but will make an exception for camping. One of the reasons my kids would want to go camping was so they could have the little boxes of crappy breakfast cereal that I'd otherwise never let them have at home. LINK