Legally blind here....along with brother and aunt, so we all grew up with it.....all juvenile macular dystrophy.
I think I would suggest not treating the child any differently than the others. My parents and grandparents did that and we're all pretty well-adjusted.
The kinds of services like Braille and even state vocational rehabilitation depends on the state. My aunt lives in Alabama, home state of Helen keller, and they provided amazing services, until budget cuts kicked in. She got an adaptive computer loaded with low vision tools, training for it, Braille instruction, CCTV and skills training for running her own business. She and my uncle run a very small business.
Here in Georgia? BIG difference. I couldn't even get help for adaptive technology in high school because my parents made too much money. (We were middle-class, by the way.)
The Library of Congress has a library for the Blind and Physically Handicapped that offers books on tape. My aunt even got one of their series on piano playing and was learning to play a little bit.
Something I found on the BBC Radio that I have LOVED has been a series on how blind people see beauty.
http://www.bbc.co.uk/programmes/b00dhkrp
Also, please don't assume that just because a person loses vision that other senses somehow get better. Most of the information the brain receives through the senses is visual and that's what the brains pays closest attention to. When there is vision loss, the brain just focuses more on other information streams. I actually had a lady lecture me and swear that my other senses were somehow superior to everyone else and that I should be able to hear or smell things better than others. I don't. I may notice things quicker but that it.
And if your friend's child does have R.P, there's a lot more out there than there ever was as far as information, support groups and even treatment. I have been affiliated with the Foundation Fighting Blindness for years and they offer support, information and even sponsor important research.
http://www.blindness.org/
I think it's great that you're curious and I hope the Mom in this situation can find some comfort in dealing with it. I will never forget the day we came home from the eye doctor with deep suspicions. My Mom went upstairs and was crying on the phone to her Mom. I was 8 years old and felt like I broke her heart. When my brother's diagnosis came in, she blamed herself and went through a very tough time. My Dad's relatives didn't help, since they also blamed her and said this wasn't in
their genes. My Mom's sister also has this, but she was only correctly diagnosed after we were, but this disease is recessive, so it took both my parents having the gene. My Dad's folks are still mostly in ignorant denial and it remains a point of contention. But mostly, we are all accepting and adjusted and just live life a little differently and that takes time and coping skills.
I still hate and get lectures from strangers in public about forgetting my glasses or telling me to go get contacts or "that surgery". Gee....wish I had thought of that.....

My other pet peeve are parents who let their children gawk, stare or try to grab my white cane when I have it and go so far as to give ignorant answers to their loud, curious questions about me as if I were deaf, too. I'm all for and have engaged in positive teaching moments and exchanges, but sometimes it's just pointless.
I've rambled quite a bit, so feel free to PM me if you want to know more.