I thought this might be worth getting out of the way from the outset... World Adventure Kids is NOT a coursebook.
I state this only as an interesting reaction to some feedback from a very respected friend (and abundantly able ELT writer) who took a look over the new version of World Adventure Kids for me yesterday. He expressed some mild surprise that the release seemed to have shed all of its supplementary comprehension and language building elements.
He was referring to one of the very first drafts of WAK which I showed to him more than two years ago. That draft featured a page of vocabulary building and comprehension/grammar questions for every page of reading text. It was, essentially, something along the lines of a reading-coursebook; and I was doing it that way because the major ELT publishers I was approaching with the idea at the time had made it abundantly clear that that was what they were hoping for: something that could be marketed and applied as a coursebook.
This IS rather interesting to me, because as soon as I stopped trying to please major publishers and looking for something that could sell in the squillions, a good hard look at the original notion and feel of 'adventure reading' reminded me that exercises and language tasks were the last things I really wanted jammed into World Adventure Kids narratives.
Admittedly, I am finishing up post-reading comprehension quizzes for each of the two adventures, mainly emphasizing the content/subject elements like science, geography and history. I also have language-oriented quizzes in the pipeline. The key difference, however, is that I want them to be optional extras to the main stories, and if they are to be applied I would encourage that they happen after a full uninterrupted reading of the texts. This to me is more of a revisiting and reviewing process; I don't want that stuff to be compulsory and I certainly don't want it jammed alongside the main story content.
Personally, I want the adventures and stories in World Adventure Kids to be experienced and enjoyed basically as they are: straight up stories. Sure, learners might like to use a dictionary to look up the meanings associated with new words or turns of phrase (and/or invite teachers and peers to help them in this process), but this should be about helping them to continue reading (not stopping and in many ways 'leaving' the story to do other stuff).
The best follow up to the stories would be discussion and small or large scale project work, further exploring a theme or task based on what they read about across entire (short) stories.
I'm not going to be so arrogant as to tell you how to use any resource in sort of black and white terms. However, I would reiterate that WAK is about stories, and I hope you find the best way to help learners experience them as stories.
That could well mean (gasp!) letting them engage with it on their own and on their own terms, helping or assisting them if and when they ask you to.
Really, when was the last time you just let your learners READ... without reading it out loud, without dissecting and analysing all the language the moment it pops up on the page?
Sure, go ahead and do content/comprehension/language work later through a second or review reading stage, but first (and this is just my personal take and preference):
Let 'em just READ, dammit!