A great video by Wylie Overstreet and Alex Gorosh.
I even do this every now and then myself just for fun and I get a bit of exercise in the process. I don’t do it quite the way Wylie and Alex did as I just pace off this distances but even so, it is very interesting.
This is a GREAT activity for children! Depending on what scale you use for distance you all you will need is a flat piece of ground, like say a football pitch. Even at one step per 10 million kilometers you can get a pretty long ways away from the starting point so plenty of room is helpful.
You can change the scale to fit your needs as long as you are looking at distance and not necessarily planetary sizes; also a good exercise for youngsters to exercise their brains during the school holiday.
To get you started have a look at this page from the Lunar and Planetary Institute.