You could put them in your mash like doing a pulpkin ale. Or you could pulp them and add the banana-water post boil.
I pulped three dozen bananas in a mesh bag for a banana mead. I did it at 160F to pasteurize them too. I wore silicone gloves and used a potato masher.
Do you want to kill a snowman?
On deck: Barleywine, Belgain Golden Ale, Hazelnut Sweet Stout, IRA, Wit, Uinta Hazel Clone, Uinta Yard Sale Clone.