First Aid Kit: Sunscreen, Bug Spray, Light Hat or Bandana - This is to help protect the head from the sun.
Mist Spray Bottle - If it is hot outside you can put a small spray bottle in a pocket on the outside of a pack so a hot child can spray themselves with water to cool off.
Water Bottle - They make small water bottles specific for children, but I prefer a regular sized one since children can drink as much water as an adult often times, and this will help prevent dehydration. I also bring along a water filter that is used to pump water from a stream, which the kids think is great fun, and allows me to keep their water bottles filled up.
Snacks in Plastic Bags - It is a good idea to carry a bunch of little baggies with snacks in an easily accessible part of your pack. Children often do not give warning of when they are getting hungry, and by the time they announce they are it is nice to have a quick stash of food for them to munch on.
Shoes - Make sure these are good quality and broken in before the trip. Bring along a blister care kit just in case.
Children Sized Backpack - If your children are 6 or 7 years old they can start to carry some of their own stuff. They make children sized backpacks with internal or external frames, and most of them adjust to fit kids up until they are into the small adult sizes. If you child is old enough and you opt to have them use their own pack, make sure that they do not carry too much, since this can injure them as well as guarantee that they will complain and not enjoy the trip.
Extra Clothes - Kids are more likely to get dirty and wet when backpacking, so it is a good idea to throw in a couple of extra shirts and socks. Make sure their clothes is a good quality. If you would not wear cotton, then do not buy cotton for your kids to hike in. It may seem like a lot of money to spend on fancy clothes, but it does not need to cost a lot. Your kids will outgrow these items, often times before they are worn out, but so will other kids. This means that it is easy to find secondhand backpacking clothing for kids by going online or looking in stores that sell gently used clothing.
Extra Food - Bring more food that the children would eat at home. They are getting a lot of exercise, burning more calories, and this often equates to a much larger appetite.
Sleeping Bag - There are many sleeping bags on the market designed for kids that have all of the wonderful features of adult sized bags. This is a great way to go, but can be costly if they need a new bag every year. Another option is to buy an adult bag and stuff the bottom with extra dry clothing. This way the child can grow into the bag and a new one does not need to be purchased every year.
Hat and Gloves - Even if it isn't the time of year where you would bring a hat and gloves for yourself, it may be a good idea to bring them along for the kiddos. This is especially useful if they are sleeping in an adult bag and need the extra warmth at night.
Long Johns - Long johns are great since they can be worn under pants, shorts, or by themselves for sleeping in. They are compact, not taking up much space.
Walking Stick - While this is in no way a necessity, many kids will find having their own walking stick a fun addition.
Binoculars - Another fun addition that can entertain kids for quite awhile.
Flashlight- It is a good idea to provide each child with their own flashlight and backup batteries. They have fun with them at night and if they wake up scared they have easy access to light.
Using this backpacking list for children, along with consulting other books and resources, will insure that you have a successful time backpacking with children.