Do I need legal permission for photographs?

To take them I mean. And like written permission.

So Amy, Sara and June want their photos taken and I will be posting them on FACEBOOK.

Amy says I can come take photos of her at her house in the babies nursery. She has a toddler and is pregnant with another. We will take Maternity photos.

Sara has an infant and wants their photos taken at a local park.

June wants photos of her taken with her puppy and cat inside her bedroom and outside.

They All verbally told me I could do this. Do I also need their written permission since I will also be taking photos of their children?

And Sara wants some of the photos edited and put on a CD so she can go to Walmart etc to print them off. If they are in BLACK AND WHITE SEPIA AND AN OBJECT IN THE PHOTO IS COLORED WHILE THE REST IS BLACK AND WHITE AND IF SHE GETS IT PRINTED OFF AT WALMART AND THE QUALITY TURNS OUT BAD OR THE MACHINE AT WALMART AUTO CORRECTS THE PHOTO I DON'T WANT TO BE LEGALLY LIABLE FOR IT BECAUSE MY CAMERA IS FINE AND TAKES GREAT PHOTOS. I HAVE A NIKON D3000

Added (1). Sorry I didn't realize some of the above was in caps

You don't need written legal permission to take the photos. They asked you to do it. So that's all you need. What happens with the photos afterward is another question altogether. I have heard that some Walmarts will not print photos if they think that they were professionally done and the customer does not have a letter from the photographer (who owns the copyright) giving them permission to print the photos. Also, you (the photographer) are somewhat limited in how you can use the photos. You can't use them to make money directly unless you have a model release from the subjects who are identifiable in the shots. Most publishers will demand a model release if you're thinking of going that route. Generally, you can use them for your portfolio or to promote your photography business. However, it's always good form to ask your subjects if you can use them in this way, especially if there are children in the shots.

As for Walmart messing up the shots, you can always point to the image itself. I don't think this is a major risk.

You have permission as they have all ASKED you to do so and it will be very obvious from the images that they are done willingly no matter where they are taken.

YOU can't be held responsible if a third party such as walmart screws up the prints.

You DO NOT need any legal documents to post them on facebook or to use them to promote your (potential) business. Although as has been said before it is useful to get a release even when it may not be a legal requirement.

These have all been asked and answered previously.

you have already mailed me querying the answers I have given previously and I have sent you a link to a PDF of Legal rights of Photographers which covers most of this.
It does not cover the printing because anyone would realise that is NOT your issue.

I have also advised you to visit the library or a bookshop and look for the necessary books which will cover the subjects you are continually asking about.

I have been mailed by a couple of other users you have also sent rude mails to when they have tried to help.

You are asking these questions on a worldwide site so it is obvious that you will get answers which may not be relevant to your country or even state in the US.
However, some of us are fairly well versed in the laws in Europe and the US because we have been working those markets for 20+ years.

If, as has been the case so far you choose to argue the toss with those who give you informed answers then that is your choice.

I for one will not be responding to any more of your questions unless you choose to apologise.

No doubt this will prompt another rude mail and probably being blocked. Ce La Vie.