I think it's really important that you can be open and honest about having GAD. It's such a misunderstood illness, so any time you can educate someone is a great opportunity to dispel some prejudice. I talk to anyone and everyone about my GAD. I find it really cathartic, and most people are just curious to learn more. Sometimes it can change things, but then, so can getting a haircut or tattoo. It's a part of you, and if people can't accept who you are then you shouldn't be worrying about how they will treat you after you tell them.
If you decide to tell people, you don't have to make it a big deal. Like, there's no rule that says you have to sit everyone down together and have a meeting about it. You can just drop it into the conversation if you feel like an opening presents itself. Like, if you are watching tv and someone does something that would make you anxious, you could just comment on how your anxiety would be too strong for you to be able to do that. It could kick of a conversation and you could find out you're not the only one struggling with it. And you need to remember, people will make it as important as you make it. If you are casual and forthright about it, so will they be. If you are stressed and nervous and uncomfortable, they will end up the same and will think it's something to be avoided.
Ultimately, it's probably better that you tell them, even if it's just so that they can understand what is happening if you have a panic attack. Think about how you would feel in their shoes. Wouldn't you prefer to know why someone is panicking if they are around you, or in your house? The more you build it up in your mind, the bigger problem it will be. Relax, take a few deep breaths, and remember that everyone suffers from some sort of stress or anxiety at some point in their lives.