Don't worry, the banana smoothie won't over-protein you. I have medium to coarse, low porosity hair, and I use WAY stronger protein treatments than that!
The only way you can know if you hair will like a treatment is to try it.
Since it's your first time trying this one, just leave it on for no more than 30 minutes and don't apply any heat. If that has no effect, then you could try a longer application in the future (and possibly steam it or blow dry during application to increase absorption). Hope it works out for you! Sounds like a great recipe.