You can make Ice cream with just frozen bananas! Blend it together for 5 minutes (with a little water if you want to make it more creamy)... it's so good!!! I heard some people add dates or nuts, but I like simple!!! :)
When I had a Champion juicer I liked to run frozen bananas and berries through it to make berry ice cream. Frickin good. I imagine you can do the same thing in a high-power blender like a Vitamix or Blendtec.
It works in a Blendtec, but I find it needs a little water in the bottom to get going. Although the motor is quite powerful, it does strain it to break down the completely solid bananas. I prefer the consistency of banana icecream from the champion. It comes out just like soft serve! Soooo yummy. Just don't eat it too fast other wise you'll get a brain freeze and a tummy ache.
I recommend that you avoid store bought ice creams. They are very high in fat and most of them use processed sugars like cane sugar or agave. Definitely avoid the soy ones at all costs. Coconut Bliss brand is vegan and seems to have to most natural ingredients and I think it's all organic...but uses agave as sweetener and is very high fat. Stick to banana icecream and never look back...it's much cheaper too!
He's probably unaware of what exactly low fat raw veganism is. The best we can do is inform him of the harmful effects of processed high fat foods, and steer him in the right direction by offering tasty alternatives that are health promoting rather than health diminishing.