Join Date: May 2008
Location: St. Albert, AB, Canada
It sounds to me like mom is a true feral - meaning she's not comfortable being around people. That means if the kittens stay with her they'll learn to do the same thing.
I agree that trapping the kittens is the best thing, but what to do once you've caught them depends on your local resources.
Feral kittens aren't really adoptable right off the bat, they'll need to be socialized and that can be quick and painless, or a long term process. It depends on how old they are mostly.
If you've just started to see them they'll probably be between 4-6 weeks, but maybe as much as 12 weeks. If their eyes are blue it'll be closer to 4 weeks, green and they're 6 weeks and up. The younger they are the easier it is to socialize them (although socializing older ferals is possible, it takes a TON of patience).
If you don't have the capability to foster them and tame them yourself (an empty room you can dedicate to them and time you can use to socialize them, as well as other normal cat supplies) Then you could try calling the local rescues to see if they know a group that can handle feral kittens.
If you have no luck then the best thing my be to TNR them, and mum. TNR stands for Trap-Neuter-Release. So they would (likely) stay wild, but be unable to make more little wild ones. If there's no way you can socialize them then this is the next best thing.