Oh my goodness your husband would have a coronary at my house. My 11yo DS still sees my breasts daily and I'm not even nursing anyone anymore :LOL We are very open with our bodies around here, it's a small house with one bathroom, modesty is just not feasable. I don't know what we would do if we were a family of prudes, there are often three of us in the bathroom at a time- one in the shower, one on the toilet and one brushing teeth or shaving or whatever. I have never hid any part of my body from my kids but I will if they ever show signs of being uncomfortable. My boys aren't shy either. I taught them to be modest around others but in our immediate family we are pretty open.
Back on topic, your poor DH needs someway to understand how natural and normal breastfeeding is and thet the boys will suffer no ill concequences from seeing your breasts while you nurse. None whatsoever. I think it is sad that he has those feelings nomatter where they stem from. Don't you stop showing your boys what breasts are for and how babies eat. It is a great part of their education as men, we want adult men who understand what breasts are and, no offence, don't end up another generation like your DH who thinks there is something wrong with what you are doing. Your DH needs to learn, will he read books? How do you think you can introduce the information to him? He really needs a re-education. I hope I don't come across harsh, I just think you are 100% right and he is 100% wrong. I hate to say it like that but it's how I feel about it.
Oh yeah, and BTW, I always nurse nomatter who is around. I don't act differently (about nursing, I do get dressed otherwise when there are guests over) when other children are around. If they haven't seen a baby nurse than I figure it is a great lesson for them. If they are wigged out by a breast, which I have never EVER seen, I would discourage them from watching but if they have a problem with it then I think there is something wrong with the education they are getting. I would never show nudity in ANY other way to other children, but a baby eating is just a baby eating, it is as natural and as innocent as it gets. I am amazed that people would have a problem with their kids seeing it but whatever, it's just going to be more ignorrant adults for our own kids to have to cope with while trying to breastfeed their own children someday. Sad.