I don't think it tastes to well as the nurses had us mixing it with ice cream and pudding for my dad. If you son is lactose intolerant those ideas won't help either.
I use a hypoallergenic plant protein powder almost daily that has great nutrients. I mix it with fruits or peanut butter and always put in a banana, as I like them and they are good for you. It supplies 42% of the daily required protein for an adult and is great for our cells. It is called PlantFusion. If you go to their website and key in your zip code it will tell you where it is for retail sale in your area. You can also buy it on Amazon. My nutritionist put me on it. No milk, nuts, soy, gluten or any thing else people are allergic to. It comes in different flavors like vanilla and chocolate. I mix it up with whatever I like in the blender with ice and coconut water. You don't need the coconut water but it is great for hydration.
Just another suggestion. It has to be hard and I know you don't have the time to run around shopping!
Hang in there