I know the end result will be the students creating their own children's book, but i need to plan 5 or so 90 minutes lessons leading up to that... what are some ways to analyze children's books and keep 8th graders engaged for 90 minutes?
First of all, the 90 minutes will likely be broken into 2 45 minute classes. Most periods are around 45 minutes of actual instructional time. So you'll start a lesson one day and finish it the next. I would choose a book that you love, and focus on the basics: setting, characterization, plot and theme. Since it's 8th grade, they'll be familiar with these but need review. Make it interesting. Create one lesson to introduce the book, and maybe one for each element with one creative assessment.
One place to start might be in summarizing childrens stories. Something I've done with my students, and they complain, but they do enjoy it, is an ABC summary of the story. The first sentence in the summary begins with a word that begins with an a. Each successive sentence begins with a word that begins with the next letter of the alphabet. The letters x and z are at your discretion, but they're doable. This would transition very easily into the elements of children's stories.
Without knowing your final goal, it is difficult to give you specific answers. As an eight grade lang/lit teacher, I often use children's books as a way to teach specific writing skills. For example, I use some books that contain a variety of tags to demonstrate that skill. Other books I use to teach onomonapeia, sentence structure variety, alliteration, etc. With some investigation you can find a children's book to teach almost any writing skill. After reading the book, students can practice the skill by writing a copy-cat story.
I usually let one of the students read the book to the class. You'd be surprised how many students love to do this!
I would think that using stations might be a good way to approach this topic. I would identify 10 or 11 items that you want students to get out of the unit. If the end goal is for them to create their own sample of children's books, you might want to reflect on items that you think they need to know in the process. Creating each item to have a station and then giving them guiding tasks or questions to discuss or complete in small groups might be a way for you to cover a great deal of ground in a comprehensive manner. Each station could last about ten to twelve minutes and this would also allow you the chance to really engage in strong discussion on a more personal level. The challenge is that it is something for you to monitor and roam about in trying to engage different groups into different discussions. Afterwards, having a reporting out might also be good where different groups talk about different experiences at different stations.
Lots of interactive activities! Ninety minutes is a long time even for high school students, so the key is to break up the time into smaller chunks. Role-playing, collaborative groups, film-viewing (sections only), debates, close-reading (quotes only), story mapping, and book talks are some activities that you might use during lessons on children's literature. In terms of content, start with broader, easier topics and work down to more specific, harder topics. Transitioning between activities will be key, but the variety will keep students engaged for such a long class period.