With two and three year olds, you can't really call it....OH LOOK A PINECONE! You walk at their pace and OH LOOK A BUG!
When they're about four or five, you can actually start to cover some distance, but you need to get into the right mental frame. If someone starts dragging, ask him/her if they want to be the leader. That often perks them right up. Little snacks of peanuts, raisins, etc. help too. If you can keep morale high, you can cover some ground. Let someone get tired, hungry or cranky and you're in for a long day.