Bring mom and kittens in, give them a warm, safe spot with blankies and see if mom does better in there.
DO NOT GIVE KITTENS (or cats) MILK - the majority of cats are lactose intolerant and will cause (sometimes) serious intestinal issues.
Get some KMR (Kitten Replacement Milk) in powder form if you can (they prefer it - you mix 1 part KMR and 2 parts water), get yourself either an infant bottle (and snip the end a bit) or a feeding syringe from your Vet. (This is only if mom is not feeding them, by the way). Hold each kitten in the crook of your arm, place syringe or bottle in through side of mouth and pointing back towards throat and do little squirts at a time. Once they are fighting back like mad and spitting it back out, they are done. Then get warm damp cloth and gently rub their poopy and pee-pee areas and place them in the litter box (this is how you litter box train). The need to be fed every 2-3 hours, 24/7 up to 8 weeks.
Be sure to get them into a vet for their 3-in-one vaccinations, rabies shot and to have mom spayed when she's done feeding (usually at 8 weeks. If she's not feeding them and you are, please e-mail me for further information on how to wean the kittens from the KMR which starts at around 5 weeks).
Animal Services Volunteer/Foster
Red-Cross Certified in Dog & Cat First Aid
Guardian of 9 Beloved Shelter Cats >^..^<