How big is your dining party? In my experience, this far out, you stand a very good chance of getting a dinner ADR, especially if you are a party of 4 or less. Persistence is key. Check whenever you have the chance. I've always managed to get an ADR, even for last minute trips. The only time I couldn't get dinner was for a party of seven two days after Christmas a year after BOG opened. We had lunch instead. It's honestly easier to get BOG after 180 than it is to get Ohana.
I do think dinner is more special than lunch, more "formal", as dining in a castle should be! Plus the beast is there. Since I've been there quite a bit now, my preference has switched from dinner to ppo breakfast. But for a first timer, dinner is essential, I think.