The parents were looking for a handout when they found you.  I'm sure they
can teach the offspring how to find another host.  Or, you can round them up
and give them to an adoption group or ... take 'em with you.

It would be sad to leave them to their own devices (foraging for food) if
you were to move. Could you catch them, spay/neuter, and bring the kittens
in (at least) for adoption?
Gail

They would probably be trapped and killed by Animal Control.  Ferals are
classified as wild and unadoptable by most Animal Control agencies and
shelters and immediately killed upon arrival.

Why not simply trap the cats, neuter and release the mom and try to find
homes for the kittens?  Feral kittens are usually quite tamable-- some adult
ferals are, too- especially females since they usually have smaller home
ranges than males.  Many areas have mobile neuter clinics that neuter ferals
free or at substantially reduced fees.

You could also contact a feral cat TNR (trap/neuter/return) group in your
area for help.  If you let me know your area, I'll try to locate a group
close to you.

You could probably borrow a livetrap from your local shelter or animal
control agency; some require a small deposit which is refunded when the trap
is returned.

Phil