Photo Ready, Set, Click!
Give them a challenge to take photos of (for example):
All the red things they see on a walk, or
Ten things beginning with W, or
Five things that move, or
Ten patterns, or
Different ‘bags’ as they walk through town, or
Refections, or
Natural lines, or
Man-made things made to look natural, or
Anything smelly!
etc etc
Set a time limit or just give it as a challenge for however long the walk lasts and review the photos at the end.
Ready, set, go!