As you might be able to tell from these pages, my wife and I are avid hikers / backpackers. We were determined that our kids would grow up thinking camping was a normal part of their lives. So, we took our daughter Akilah camping when she was 6 months old. We drove up into the Pecos National Forest and camped near a stream. No problem!
With a kid you do have to make some adjustments. We couldn't carry our backpacking gear plus her, plus her stuff. Instead, we explored 4WD areas where we were car camping, but in places where we might see 3 people in 2 days. We just pulled off in the forest and camped. We could still go on relatively lengthy day hikes, if we were willing to carry her. At this point, camping is one of her favorite things to do. She also loves maps as shown in the picture below where she is studying the topo map with me.
As I write this, Akilah is not quite 3 1/2 years old. We just got back from a trip on which we did a 13 mile and a 7 mile day hike. On both of those hikes she hiked 4 miles herself. A couple of years ago I met a couple backpacking with a 5 year old. They had gone about 4 miles a day and said it was doable but about their child's limit.