Teaching Your Child the Arabic Alphabet (AbiHomeschoolsToo.com) - A nice article with tips for teaching the Arabic alphabet to kids, as well as a suggested sequence. I've always taught my kids in alphabetical order, but he makes a good point that some kids have a difficulty distinguishing between the letters that differ only by dots.
I've also got a complete set of lessons for teaching the alphabet to preschoolers/lower elementary over at my old wordpress blog (https://talibiddeenjr.wordpress.com/category/arabic-alphabets/page/3/). Here, I teach in alphabetical order. They are spread out over several posts, so you'll need to scroll around a bit. In shaa Allah, I hope to put them into a PDF file for ease of use.