Newborn kittens are extremely fragile creatures. Once the kittens are weaned (around four weeks old), a friendly mother may allow you to interact with her babies. Let the mother set the limits for this interaction. Notice her body language and respect her wishes if she becomes agitated. A rapidly swishing tail is a sure sign that she's had enough. But what if you notice that the kittens have fleas? Maria L. writes:
Maria, we recommend that kittens not be bathed until they are at least eight weeks old. Until then, the mother should be their exclusive caregiver. She will bathe them and even stimulate them to pee and poop since they're unable to do this on their own.
After eight weeks, you may bathe them using just warm water. Even Dawn dishwashing liquid, which is used by some animal rescue groups, may be too harsh for kittens. Soap really won't help anyway. Warm water and a flea comb are the best choices. Dry them thoroughly with a towel and never use a hair dryer. If it's cool outside, keep them in a warm place until they're completely dry.
You shouldn't use any flea control products on kittens as the chemicals will be much too harsh for them. They could actually damage their sensitive systems. Yes, the fleas will come back. Just clean their bedding and bathe them periodically until they're old enough for flea control.
Once they've grown to a weight of five pounds, see this post for flea control options. You'll also want to get Mama Cat spayed so she doesn't produce more kittens. Since she's friendly, she'll probably be adoptable too! Good luck!