4 Week Old Stray Kittens, moved by mother or dead?

4 weeks ago a semi feral cat that my family feeds gave birth to 4 kittens. We found her kittens in our barn, about 500 feet from where we feed her. About 2 weeks later she moved them much closer into the woods about 50 feet from where we feed her. But then we had some painting done on the outside of our house and there were workmen and trucks in that area so I think she moved them again, but we haven't been able to find them yet. I'm wondering now if they're alive. I've tried following her a few times, but she runs away. Because shes not super friendly to begin with I can't tell if she's being secretive and trying not to take me to the kittens or if she just wants me to leave her alone. We have 10 acres of property and its mostly woods. There is also a steep cliff behind our house and but there are a lot of ledges and I have seen her walking down on them quite a bit recently, so I think the kittens might be in a cubby hole down there. I obviously want to get to the kittens so I can socialize them and find them homes eventually. My questions are these:

Would she put the kittens on a ledge of a cliff or would she know they might fall?
Do you have any tips of finding kittens?
Will she bring her kittens to the house to eat when it's time for them to start eating solid food?

I'm hoping she will bring the kittens to us soon, but I don't know if that's something that happens.

Yes, from my experience with feral mama cats she'll start bringing them around when they're about 6 weeks old, to introduce them to solid food. If she trusts you she might let you pet them at that point, otherwise you might need to trap them somehow while they're still young enough to socialize. I have also found that they do tend to move the nest after a few weeks, whether that's because the area got dirty and she doesn't want to attract predators, or because the first nest area wasn't suitable for mobile kittens, I don't know.

If you hang around the area she goes to, you might be able to see the babies playing on the rocks.

Make sure you find a way to get mama cat spayed or you'll be doing this twice a year!