My kids are much younger (not quite 3, and not quite 1), but we get out there as much as we can with them along. Most recently, we spent two entire months on a wilderness expedition on Malaspina Glacier (southeast Alaska).
Paradoxically, I find it easier to get out for long expeditions than short backpacking trips. It seems like the planning and gear required to get the whole family out is similar, but the logistics to reward ratio is better for longer trips.
If we want to go very far, we need to carry both kids (50 pounds combined), so it requires both parents. (I'm impressed by anyone carrying 60 pounds of kids by themselves! I can carry both mine, but it's not a lot of fun).
Between expeditions, we do a lot of dayhikes. We have the advantage of living with wilderness on our doorstep, so it's easy to do. It also reduces the motivation to get out overnight, especially in the very long nights of an Alaska winter. If I go by myself, I go at toddler pace, or try to go somewhere where I can bike/sled to get to where he can walk. With both parents, we can mix faster/farther travel with toddler exploration.
We are attempting to "train" my almost 3 year old, but can't get him to walk nearly 4 miles by himself yet (at least not all in one shot). Possibly because the 10 feet per hour pace that comes with a kid wanting to investigate, explore, and play with every single stick along the way means that it would take superhuman patience to get that far.