My first reaction to your initial post, kcc, is to also recommend that you both read as much as you can about polyamory, ask questions here, and keep talking with him about how he would envision things. And decide for yourself whether it is something you want. Don't just get into it to make him happy, because putting your own needs aside will make you miserable. Make sure you are both as informed as possible, and then take baby steps. Don't jump into being sexual with other people right away.
As far as telling your parents... um, why would you? You're an adult, and poly is just something you're considering now, to see if it is right for you. Why should they be told anything that is private between you and your boyfriend, when it would probably just create drama and ickiness, especially if they are not as open-minded? I would wait a while until you actually have a poly relationship happening, and it's got some stability, before you start telling your parents and rocking the boat.