Its not just moving swiftly to be safe but you need to move SILENTLY and as unobserved as possible, with kit rattling, kids talking, clothes rustlings, panting, wheezing etc in an environment devoid of noise creating vehicles a family will make a lot of attention attracting noise.
Shape, Shine, Shadow, Sound, Silhouette, Skyline will all get you dead. It does not matter how fit you are, or how much gear you can carry, or how tough you are, or how well armed you are. If you are SEEN it only takes one kid with a single shot 22 rimfire on his home ground to get lucky and you are buzzard food. Firepower and Speed are for when things go tits up, silence, stealth, non detection are what sees your WHOLE group get to your destination.