Reddit reviews Pretend Soup and Other Real Recipes: A Cookbook for Preschoolers and Up

Amazing cookbook for preschoolers (has every recipe "written" in pictures for kids to follow and then repeated in writing for adults): https://www.amazon.com/Pretend-Soup-Other-Real-Recipes/dp/1883672066

Also I think making guac or fresh salsa is super fun for little kids, and also anything where they get to pour stuff through the hole in the food processor and watch it get squished.

As a preschool teacher I cooked with the kids about 2-3. We made fruit salad, guacamole, pancakes. Also for other ideas you can get some cook books for kids: http://www.amazon.com/Pretend-Soup-Other-Real-Recipes/dp/1883672066/ref=zg_bs_2655476011_16
I own the one above and they have really cook step by step drawn pictures of how to make the food which really help kids because of the pictures.

I'm not sure if your dad was planning on just text recipes, but one of my favorite (cook)books when I was little was Pretend Soup, it was vegetarian not vegan if I recall correctly, but what I really liked was that there were cute little illustrations of every step in the cooking process. This made it a lot easier to figure out what to do, especially when I was just learning to read. Some of the recipes I remember enjoying were "popover" muffins with a strawberry in the middle. Just in general I think breads, muffins, cupcakes, etc. are more fun than something which involves a lot of chopping and use of knives depending on the kids age, may not be something they can do. So I'd go with more simple recipes, pancakes seem good.

Made me think of this. Dunno if that's where the inspiration came from, though.

Teach your kid to cook.

I highly recommend this book that I had as a child.