Just an extra line of code to above which is helpful. After you have your childBP ref (UBlueprint) you can make it more usable with:
bp_gc = ue.EditorAssetLibrary.load_blueprint_class(childBP.get_path_name())
Which will give you the BlueprintGeneratedClass
Then if you wanted to change data on it, you can get the cdo by:
bp_cdo = ue.get_default_object(bp_gc)