I try to do most of my book buying around this time of year, or in June at a large book sale, since a lot of families are selling this time of year. I do most of my pre-reading now after the books start to come in and decide on what I’ll keep. Then, I try to do my real planning in July when my dc are either at church camp or VBS.
I don’t plan out every detail, but I like to have my SCM materials ready like, picture study/shakespeare, that we plan to use. We’ve been using Ambleside’s years so the book choices are already made, to a degree. I’m still pre-reading them before I make my final plan and even then they may change a bit by the time the school year begins.
We are a participate in a co-op and I usually wait to see what may be taught there which can sometimes change my plans, but that’s ok. I try to be flexible.
I don’t like to spend my whole summer planning, either, so I do what I can now as the year is winding down. But honestly, as homeschooling moms, I think we’re always in plan mode, at least I feel like I am sometimes.
HTH