I have a kid book with text and pictures. I made a Word document and saved as .doc. I had no fancy anything and used page break between the text and pictures. Some need to use section break. The Nook preview was something to see. Everything came out the right way. It was my first time uploading an ebook. Simple methods usually work well. I also used the same document to upload at Kindle. It worked. I do have a PDF version that I converted with a free online application and the text is at the top of the page and the pictures are what they were before. I did that for my blog so that the book could be downloaded and printed out. I have no idea if any if any of my garble helps.
What you are talking about is essentially nook kids. They have a special way of designing for that and you need to be approved with them to do so. Involves an NDA and distribution agreement to get into the nook kids channel. It is aimed at exactly what you want, a fixed layout title, you can include narration with the eBook as well.
Hope that helps, they don't let a lot of people in, I have access and I know of about maybe a dozen others that do, that includes the big 6 pubs that have access. They keep it pretty closed up.