Hello and welcome!
I own a few plant identification books, but have yet to find the perfect one. I do suggest looking for books with drawings rather than photos.
I’ve discovered after starting my own nature journal that drawing the flowers myself has been the absolutely best way to learn how to identify the flowers. I might not know what I’m drawing at the time, but once I have drawn the plant, it’s much easier to spot it in a reference book. It’s almost as if the plants pop out of hiding on the page for me after I have drawn them.
I looked at Asiatic Day Lilies in the wild for ages and I’m sure I saw them in the books I own, but I never identified the plant. I drew the flower on a whim one day while picnicking and then I spotted it immediately on a plant identification card I carry with me. I nodded as I read the description because after looking at the plant so closely to draw it, I recognized its characteristics easily. Drawing not only forces you to look at something, it also helps you to understand the essence of the flower and to remember the details.
Even if your kids aren’t interested in natural journals yet, though they might be, bring along your own paper and pencils and sketch what you see…if you aren’t doing that already.
I have a book with large color illustrations. It’s called An Introduction to Nature: Birds, Wild Flowers, Trees by John Kieran. I found it at a thrift store and I’m not sure of it’s availability. The descriptions are short and engaging. However, it’s large book and not good for carrying in the field.
Have fun!