Al-Anon and Nar-Anon were around way before the Internet.
I don't think I'd particularly want my parents on the same forum where I post. I suppose you could tell them there are lots of resources on the Internet, and if they happen to come here, then they do.
Or if you don't think it would bother you for them to read about what you have posted, then go ahead and invite them. I guess I feel like if they found it on their own they might be less likely to assume you are on here, too.