python:从JSON中提取所有特定的子键

如果我有如下类似的JSON:

"children": [
        {
            "firstName": "Alice",
            "age": 6
        },
        {
            "firstName": "Bob",
            "age": 8
        }
        {
            "firstName": "Candice",
            "age": 4
        }
    ]

我想要一个包含所有名字值的数组,我该如何用python获取它们?

我尝试过以下方法,但我的数据集较大(40000行),重复它是不切实际的:

children = JSON

firstNames = []

firstNames.append(json.loads(children.text)['children'][0]['firstName'])
firstNames.append(json.loads(children.text)['children'][1]['firstName'])
firstNames.append(json.loads(children.text)['children'][2]['firstName'])

我已经考虑过使用for循环来替换这些数字,但不知道该怎么做。