25km isn't too rough unless you're copping a lot of ups and downs, or don't enjoy walking. Helps if you start early to cover ground and give yourself time to rest.
Our 4yo daughter did day hikes in the 15-20km range a few times last year, in mountainous terrain. I think attitude and resilience are key.
In this case, one advantage was the author having a 7kg pack and using accommodation/food along the way rather than carrying a tent, sleeping gear, food, 2-3L of water, etc. Starting with day hikes or walking part of your commute is an easy way to build up to trying longer adventures.
In 2021 when my other two children were 6yo and 9yo, they did 40+ km in 24 hours. Hiked midday until 10pm and then 7am until midday the day after. They are just normal kids; I am not fit but enjoy hiking.
25 km/day, flat terrain, light pack--I have dietary issues that could prove problematic for a four-day trip (expending 4,000 calories in a day, not an issue. Consuming 4,000 calories in a day would be hard--I would worry about bonking) but I fairly routinely hike 25km in a day and with nearly twice his load (I'm typically in the middle of nowhere, if I have to push the button help would likely be hours away--my safety standard is I should be able to survive the night) and rarely less than 500m of climb over the day.
A lot depends on the terrain and the condition of the trail/road. (Pavement does tend to be a bit harder on your feet than a nice dirt trail.)
25km (~15mi) per day on level terrain on a path in good condition is a good walk but not anything exceptional. If there are ups and downs and the trail is rock and rough that's a whole different story.
I was wondering this too. Last time I did a ~15km walk, my legs and feet were really aching at the end of it. I think I could have done another 15km back if I had no other choice, but it would have been miserable. As it started to rain, I got a lift back instead.
Our 4yo daughter did day hikes in the 15-20km range a few times last year, in mountainous terrain. I think attitude and resilience are key.
In this case, one advantage was the author having a 7kg pack and using accommodation/food along the way rather than carrying a tent, sleeping gear, food, 2-3L of water, etc. Starting with day hikes or walking part of your commute is an easy way to build up to trying longer adventures.