Momma cat and her 5 kittens

Hello everyone, I just rescued a momma cat and her 5 kittens. I need to get them seen soon. I believe they have a upper respiratory infection. One of the kittens has a broken leg and another is very small and im worried he wont make it without some help. Im not sure how much to request so i am asking for 500. If the vet bill costs less any proceeds will go to the humane cny. I will provide vet proof once they are seen including a final price. Any and all help is appreciated