I'm 46, with 2 grown children, 4 grandchildren and live 6 hours away from my mom. She still said no when I told her about the week-long tour I'm doing this summer. She's become used to me touring solo, but blew a gasket when she heard that I was touring solo outside of my province. She also told me that I wasn't allowed to camp. hehehe

I've only started touring this last few years. To be honest, I don't know what my reaction would have been had my 17 year old told me that he wanted to do a bike tour before I ever knew how wonderful touring was. I suspect that it would have been very similar to your parents. Don't give up on that dream, but I would slowly work towards seeing if they would agree to a weekend tour. Have them help you plan the route and where you're going to stay. Trying to force the issue isn't going to get you anywhere. Keep talking about it, planning different weekend rides, and maybe they'll become more adjusted to you doing this. Then work with them, and see what will make them feel more comfortable with what you want to do. Their minds are not going to change over night. Patience might be the big thing here.