Actually a single bird cannot feed that many chicks unless they are old enough to not require protection from predators/weather. If they were close to fledging, she might be able to pull it off because she could spend her time hunting for herself and the chicks. None of them would be very well fed, but they could probably all make it. Anything younger and its impossible for her to be able to meet everyone's needs, chicks would definitely be lost.
As for hand-feeding the chicks at the nestsite, neat idea, great that they have the access to the nest, required food, and expertise! With luck the chicks are old enough not to imprint on the people rather than Mom. I'll be very interested to see what happens .... Oh and by the way, that's a feeding every 4 hours day and night folks!!