unhashable type: dict with test JSON

The reason your first example doesn't work is that each 'child' key has a dictionary declared as it's value instead of a list, as it looks like you intended. Replace the { with [ and it will work.

'child': {
    {'kid1':'one'},
    {'kid2':'two'},
    {'kid3':'three'},
},

Should be:

'child': [
    {'kid1':'one'},
    {'kid2':'two'},
    {'kid3':'three'},
],

In other words, you're saying 'child' is a dictionary without giving a dictionary.