Can you remove the bucket from the post and move the whole works at night? If you could do this with as little commotion as possible, it might work. I have moved a few chickens and nests at night, and had pretty good luck with it. I've only had one that didn't stay on the nest. If you can't move the whole nest, I would guess that you have no choice but to leave them be. Broodies tend to stay on the nest a day or two after they start hatching, so keep an eye on them (Have all the eggs been incubating for the same amount of time? If not, and they haven't been there for long, I'd take all those eggs and give them new ones so they're at the same stages of incubation) When they start hatching, give them a day or so, then take the babies out of the nest. The mamas will follow.