I wouldn't worry about the borax harming your little ones, as it is
extremely benign as chemicals go.  I lived in the FFZ of Boron, California
for most of my life, downwind from the worlds largest open pit borax mine.
Not only did I not suffer any ill effects (I spent several college summers
working at the mine, comming home coated with the dust, etc.) but my furries
LOOOVVVEEEED to dig in the borax/sand dunes directly east of the pit, no
harm at all.
 
What your little ones will pick on their feet won't harm them a bit,
assuming it is a true borax dust, and doesn't have more harmful chemicals in
it as well.  I'd read the label and go from there.
 
David Minette
[Posted in FML issue 1549]