You could store them all in an array and then you can just use
set( hGraphics, 'Visible', 'off' )
Certainly your axes would be better as hAx(1), hAx(2), hAx(3) rather than 3 individual variables and you can tag a rectangle onto the same array too as it will just be an array of general graphics objects.
Recursively hunting through children can be a messy business although there may be functions that can do it, or something on file exchange.
A rectangle will be parented by an axes though so you can explicitly get children of your axes and hide them rather than starting at figure level.
