Infants three months or so can be taken on the trail with the proper preparation. Weather should always be carefully considered, along with the length and altitude of the hike. Backpacking overnight can begin as early as three months, but up to about twelve months, a baby's respiratory system cannot readily adjust to major changes in altitude. Your first hikes should be short, so if something does go wrong, a quick retreat can be made to car and home. As parents, you may think a one or two mile hike is hardly worth the trip, but it is a good learning environment, and you will quickly learn how much extra is required to care for a baby on the trail, without the risk of a longer hike.
Babies generally enjoy the lulling bounce of the hiker and end up sleeping most of the time.
Toddlers from 2 to 4 years old are actually the most awkward age to hike with. Toddlers are too big to be carried, yet have little stamina and cannot walk very fast or very far. Hiking with toddlers requires the utmost patience and creativity. A Good Attitude Kids may complain the whole way up the mountain or trail, only to be perfectly content and no longer tired once camp is reached. Patience will become the greatest tool for your children's enjoyment and for your own sanity.