I know that this might be a little early for some people, but I ordered this great scholastic book a couple weeks ago at a book fair, and received it today. It is called "A Poppy Is To Remember", by Heather Patterson and Ron Lightburn. It introduces the subject of the war gently for little children, gives them the "In Flanders Field" poem, and goes into a little more detail later on in the book.
This is a Canadian book, but could be used anywhere. Remembrance Day is a pretty big deal for me, as my Grandpa served in Italy during WWI and will turn 95 in February. We don't have a lot of vets left, and I really don't want to lose their legacy by making Remembrance Day just another paid day off. I just really thought this book was a great way to introduce kids to the symbolism behind it. This book is available through Amazon.ca, and shipping is free if you were to order a couple Christmas presents a little early. If you ordered soon, you could get it in time to share with your little ones.