I took DD (5) to the library today and that book was there, in one of the units we always pick from. I only had time for a quick look, so missed any subtle references/Easter eggs. The book looked quite innocuous apart from the guy in bondage gear, but at least the illustration wasn’t revealing or explicit.
Granddad misses his former partner (known as Gramps) who apparently died. So, the book is partly about grief. It’s strange to think of a young girl arranging a Pride celebration though. My DD knows that families come in various configurations (single mum, two dads, children living with grandparents etc.), but she doesn’t know anything about sex or sexual orientation, and I don’t think she needs to know about that yet.
Right now, I can’t think of a reason that a parent would need to read this book to their child. I’ve seen picture books about children living with two mums or two dads which look much more appropriate for this age group (2-7 years).