I do not mind your questions at all. It is actually interesting for me to reflect on this for I never planned this all out...it was just some of the stuff that came about naturally. So I never put much thought into it before this post.
If your son is just 3, he might just be ready for a simple explanation, and you can provide him with more details as he grows up and is more developmentally aware of certain ideas. Death is a really difficult concept to understand. We had a great-aunt die when dd was four, and even with that personal experience (she was very close to my aunt), it was still hard for her to understand. I think rather than trying to get him to understand death, it might be easier to explain vegetarianism in a different way? My dd was that age, I bought Victor the Vegetarian, and the followup book, Victor's Picnic with the Vegetarian Animals. There is also a children's book about Herb the Vegetarian Dragon, but I did not like that book when she is so little because they talked about beheading Herb
(which was a concept that I really did not want to explain to dd!!) The second victor book focuses on foods that vegetarians eat, but the first focuses on why victor became a vegetarian (he lives on a farm, and the sheep has two baby lambs who become victor's best friends. When Victor hears his father talking about wanting lamb chops, he runs away to save the lambs, and ultimately decides that he would be friends with all the animals (cows, pigs, etc) if he had a chance, so he should not eat them either. ) The message "we love animals so we do not want to do anything to hurt them" might be easier to explaining death.
I just recently started talking with dd about factory farming (after she turned five), and she was already aware that there are many people who mistreat animals. (oh, and I think I took the pictures from one of John Robbin's books)
For the circus stuff, I am a member of our local animal rights group, and just started taking her along to protests with me. We have a very, very small activist group here, so the protests usually consisted of four or five people holding up signs and passing out literature. I knew they would not get crazy or violent or anything. Dd looked at the signs (some of them had photographs of elephants wearing chains), and talked with the other protestors about their signs and why they did not like the circus. One funny thing: she thinks that clowns are in charge of the circus so she has always blamed the clowns for the animal cruelty. She will say things like "I want to tell those clowns to let the animals be free!" She also made her own protest sign that she could carry...gluing pictures of animals on and then she added tears going down their eyes. Peta has a children's group for animal rights (which is completely free!), and when we joined they sent a neat comic book about a circus elephant, and some other neat things. They also send a magazine several times a year, which sometimes has some neat things in, but for the most part is directed at much older kids. Peta also a bookstore with children's books about animal rights.
As for how to empower her? I just always try to send the message that she can make a huge difference in the world. I am an activist at heart, so this is all encompassing. I think it is very important though, for most of the animal rights stuff is very, very sad. Personally, if I just focused on all bad things happening in the world, without doing anything to correct them, then I might start viewing the situation as hopeless. But if I know that I am doing things everyday that make a difference and make the world a better place, then I am filled with hope and determination to end the sadness and suffering. Food wise, she knows that because she does not eat meat, there are animals in the world that will not have to die to feed her...that her personal choices make a big difference. She also has tried to educate her friends about vegetarianism, but that has not worked so well (little kids get too focused on who is right and wrong so we are just working on having tolerance of everybody's choices right now) But as she gets older, I could see how giving a presentation on vegetarianism in school might be really influential to others. We have picked up trash at the park to help make the earth a better place, we choose not to buy pets that have to be caged, and so on. And talk about how our choices influence people who are mistreating animals (if we pay money to the circus, then there will be more and more circuses but if nobody paid money to the circus, then the circuss would close, and no more circus animals would be kept in chains and cages. ) So not going to the circus becomes a way to help the animals.
A lot of this has been done in the last year or two though, and dd is *highly* interested in these topics (animals are her true love and passion right now), and she is also really good at conceptual thinking, which not all kids might be ready for.