Not all brooding hens are aggressive. Some of mine certainly seem to see me as a benefit to their chicks. They'll tolerate me reaching under them and call them out when they see me (likely because they also view me as the food source). Others, however, can be perfectly fine with my presence when they don't have chicks and then turn into little monsters when they do. Growling, puffing and pecking if I dare get too close. I've even had hens in the past outright attack me. I used to have a buff Orp that would give my feet a good flogging and pecking when she was broody. She was perfectly fine when not. I guess its just luck of the draw.
Your little family is super cute, and I have to say, that's a mighty impressive nest they've made!
Good luck with them!