Definitely no issue in tix selling this time of year and as of now, all parks are wide open on reservations. I'd venture to guess that you'd have no issues however, if I were you, I'd still want an idea of my plans so I'd pick a day after consulting the forecast and go from there.
I would book something..... and then change it once you know where you want to go. It's easy to change and nice to at least have something in the small chance it does sell out.....