If your bananas are not very ripe, then a little honey or maple syrup will help to sweeten it. If you use really ripe bananas, then you shouldn't need to add any extra sweetener to it.
If you want really cold milk, then you can use slices of frozen banana. make sure you use a high powered blender, as it will be harder to blend them when they are frozen. You could always add a couple of ice cubes to make it cold too.
We used cinnamon to add a little extra flavour, however you could swap it for ginger or nutmeg.