There are different opinions about this here. Kittens should IDEALLY be with mum until they're about 12 weeks old. BUT they socialize much better at around 8 - 10 weeks old. Some would just start feeding them on a schedule and trap them ASAP. We always waited until they were older, but that was because we didn't have space to foster, so if we couldn't find homes for the kittens, we wanted them to be able to survive as part of the feral colony we cared for.
If you think they're fairly safe where you live (from cars and predators), then I'd wait another couple of weeks before trapping. In the meantime, you can work on finding a shelter, a foster network, or a low-cost spay/neuter clinic, and a place to borrow or rent a trap.
Is the mom friendly - meaning - do you think she's a stray? Or do you think she's feral? It's the right time of year where you MAY find space in a shelter or room in a foster network. The kittens shouldn't be too difficult - it would help a lot if your friend does want to adopt them!

But just FYI, many shelters will kill animals they deem not friendly enough to adopt out (even many no kill shelters kill "ferals" - check the fine print, so to speak, they are often "no kill" for adoptable kitties).
Anyway, many vets and many shelters lend or rent out traps. Some just require a deposit they keep until you return the trap. When you get the trap, wash it with a light bleach solution to get the smell of cats and fear off of it. If you can afford Feliway spray, buy some and spray the trap with it to make it smell friendly. A few days before you want to first set the trap, start putting the food in the trap, but don't set it. If it's in your yard, pour dirt over the bottom so they don't have to walk on the wires. When you do set it, the trap just lifts up through it. And the day you want to trap, use a really stinky food - tuna, KFC (no skin), sardines...
In the meantime, do feed the cats, at the time you'd want to trap them and where you'd want to trap them. Put food out the same time and the same place every day for just one hour. They'll pick up on the schedule.
You can google "Newburgh, NY cat rescue" or Newburgh, NY low cost spay - and you can search at
http://www.pets911.com. It looks like it's all set up as lost pet site now, but once you get your zip code in there, you can search for shelters and low cost spay & stuff.
You can also type in your zip code and just "cat" at
http://www.petfinder.com. Go through the listings - all the cats listed have an org associated with them. Each org has contact info somewhere. You can conduct an e-mail campaign to see if you can find a shelter or someplace with a foster network to see if you can find someone to help. Just bear in mind that most places are underfunded and under-staffed, and it may take a while to hear back from a small percentage of them. We went out to a 3-hour radius, e-mailed about 22 orgs, and heard back from just 2, I think (but one did help). (We're in NW NJ). Important to note - almost all the e-mails are personal e-mails, so it really helps if you write down somewhere the name of the org and the e-mail associated with it, so when someone replies, you know which org is replying.
That's what we'd do.




Thank you for wanting to help these kitties!
... and please keep us posted!