I wonder if you might try a non-children's cookbook, one that's justly popular for a mix of relative simplicity and ease, clear and appealing pictures of the resulting dish, and predominant use of real ingredients (rather than packaged, already processed food).
Examples that spring to mind are The Barefoot Contessa Cookbook and Nigella Express. Of course not every recipe is suitable -- both those books have cocktail recipes, e.g., and it could be that Express uses more pre-prepped ingredients than would be ideal. But maybe you already have one of these or a similar book (an early Jamie Oliver, say), and could invite the 8-yr-old to pick out a couple of dishes that appeal and try one out.
Stuck inside with a bad spring cold yesterday, I watched a BC episode for the first time in many years. Not for the first time, I thought how excellent the show would be as an instructional video if reduced to the actual Ina-cooking parts. No offense to the winsome Jeffrey and his immaculate Oxford-cloth shirts, but watching him buy English muffins at the Model Bakery only stimulates in me restive thoughts about the 1%. Back in the kitchen, though, Ina erased all those with sound, practical advice (eggs must be at room temperature for blender Hollandaise, when to put prosciutto strips in the oven to finish at the same time as the asparagus, don't fry eggs at high temperature) while the camera showed each step in the process from start to finish. Yes, I know it's not cinema verite, but done with many interspersed takes; still, the result is a lot more actual, comprehensible cooking than you see on most of the cooking shows, even putting aside the competitions.
Caveat: My advice may be worth considerably less than you're paying for it; I have neither children nor either of the cookbooks I've mentioned. (Though I have checked out BC from the library and cooked several things from it.)