I'm sure I've visited that challenge before. Here are some possibilities:
Sandals with no socks?
Those jelly shoe things?
Some of those little leather baby shoes? (like http://www.bambinosbox.co.uk/soft-sole-leather-baby-shoes.html - that's not me spamming, it was just the first google hit)
Some children go through a stage where they HATE putting on shoes and socks before going out, but once they are outside smelling a flower or something, you can slip them on without the child even noticing or minding. Or leave them off till you get to a piece of rough ground and then offer the shoes.
Are you sure the shoes are comfortable? That'd lead me towards the baby shoes because they are just so soft.
I spent most of my childhood running around with bare feet, except when I was in a nettle patch or among too much chicken s**t :-)