Sandy- you will LOVE the discbound system!
Good idea on the moon phases. As for the observations- I suggest printing off extra monthlies and use them for personal purposes such as that. I use monthlies for all sorts of weird things like checking off social media posts so I don't miss days! The sky is the limit on the things you can track
I was a little hesitant to include pages that are redundant to our Plant Lists here on NGA. My first reaction is that I pretty much hate redundancy, so I didn't include them, but I'm really warming to the idea. I know a lot of people are paper based more than tech-based (I am too, but not for my plants), and also because it would give you a place to jot down notes in an organized way in the garden if you wanted to transfer to NGA later.
Keep us updated on your planner adventures!