If you can stay nearby, you could put mum into a small cat crate, then set a cat trap in front of the mesh door of the crate, so she can see and call them, put some food down near the mum, in the trap, and catch the kittens. You may have to catch them in 2 lots. If so, take the caught ones home to the safe room, let them out, and go back to other kits and mum, set up again.
You should be able to borrow or hire a cat trap from any rescue.
Could you drive 2 to 3 hours towards Grace Lily, if Grace Lily could drive an hour plus, towards you? If GL will take them, you will be financially better off, and have far less stress on your animals, if you volunteer the extra driving. Think of it as a donation to save these littlies from an awful life as ferals/strays. Shout yourselves a morning tea and a tourist gawk as a reward