well, i think i'd risk them not being w/ their mama, esp. if she is feral. you can help the babies & give them a chance @ a nice life
i'd bathe them in a gentle soap & try to get off as many fleas as possible.
one of our year old cats we have now, we adopted fromthe humane society last summer.. she was a wee bitty thing *maybe* 2w old, she had no mama so we were able to adopt her. she is thriving, so it is possible to help them.