The spoilers are the things which can go wrong and spoil a hiking trip. Enough spoilers and your children may never want to go hiking again. The results of several bites and a sunburnt neck will linger long after their memory of a beautiful wildflower. Always have a bottle of sunblock and bug repellent in your pack. Have your children wear hats and sunglasses on bright sunny days, especially in the mountains.
Blisters are usually the result of poor fitting shoes.
Find tennis shoes or light-weight boots that fit properly. Also use socks that provide plenty of cushion. Try wool and orlon materials. Bring along a foot repair kit complete with moleskin and adhesive tape. When a child first complains of a sore spot or hot spot on their foot, stop and patch it up before it becomes a full-blown blister.