I'm sorry to hear your parents are having trouble with your interest in Peace Corps. It's understandable and something you and them should definitely get information about before giving up...or simply decide not to listen to one another. I'm always up to help out and provide some insight if you're interested!
Peace Corps allows US citizens to travel, work, learn, and teach abroad for 2 years on behalf of our government and people. This is something a lot of countries don't take the time in doing/or even have the resources (money, people) to do. It's very special and unique. People in Uganda often ask how they can come to the US... I don't know??? Education, your government, volunteer programs, Church, work exchanges, NGO exchanges, family, friends, MONEY?
You should read over the 3 Peace Corps Goals, 2/3 of them directly relate to the learning and sharing of each other’s country and cultural understanding. By spending 2+ years somewhere, living amongst common people (who you will learn will be a lot like yourself), learning a bit of their language, and making the attempt to learn from someone else, while also providing them your technical knowledge and experience, is special. It's much different than spending all your time isolated and separated from people in YOUR own or THEIR country.
I had a lot of people tell me I could do this work in the US, and that the US has plenty of ppl to also help out...which is VERY true and needed. No doubt this is on my mind a lot. Maybe your family brings this up? It's important to talk about. My response to people was that this was an opportunity to learn more about the worlds needs, not just ours, and be able to bring that back to many people in the US. I told them that it was for only 2 years, and an opportunity that made since for me to do NOW. Although I heard it plenty before, I’ve learned quickly that poor in America does not equal poor in Africa, or anywhere else for that matter. Doing this doesn't mean you don't care, or don't plan on moving back to the US. I think by becoming a US ambassador (not really) for 2 years for these very different and isolated communities does a lot for our own country and its people. People I meet don't really know much about the US, and it's amazing the connection you can give them, and the satisfaction they get from learning it. I believe world relationships are something the US needs to improve, anyhow.
There's a book called The Ugly American if you're interested in reading what's wrong (or what was) with American foreign policy; it was given to me by one of my graduate professors. Good read, and it helped me understand about why Peace Corps was structured the way it was, though the book never once mentions Peace Corps. Before it’s time I suppose…
As for the reading material to explain PC to your family, I would highly suggest contacting your PC recruiter. He/She will definitely have that information in electronic form, or be able to mail it to you. I was given a hard copy of a manual for parents on what to expect, and how to cope with a child in Peace Corps. I got this when I was given my country invitation, maybe they could send this to you sooner. These questions I feel are exactly what you're recruiter should help you with.
Take care, there. I think telling your family that PC is something YOU are interested in doing and is an opportunity to learn much more than you'll ever get out of reading a book... or watching the news, will help. Again, this doesn’t mean you won’t be coming back. Be sure to tell them you’re willing to listen to their concerns as well…their family after all. Maybe after all this there'll be better understanding and some hope. I don't doubt it...and it is important to get past. I believe most volunteers go home early because of family, friends, and/or school anyhow. The two years are not easy, but challenging and rewarding (and I’ve only been here 8 months). The way I think of it, is that there's no place I'd rather be, or nothing else in the US that I'd rather be doing. Again, family is most important, and you guys should want to talk about this stuff first. I hope it goes well. Just be happy about whatever decision ya make...sounds like either of your options are pretty good ones. There's a big world outside the US, one that I haven’t even come close to seeing or feeling. I hope this initial perspective helps.