L.M.
Kale and fresh spinach may be less detectable believe it or not. Always throw in a banana, it seems to mask more. My girls like vanilla almond milk, frozen blueberries, banana, spinach or kale. But not frozen spinach or kale, it has to be fresh. Also romaine lettuce is a good idea to start with. Add water to thin it out if needed. You can make this as a smoothie, or freeze it for the pops.
Toadally Primal Smoothies by Primal Toad is a great recipe book :)