How beautiful Tucker is!
He sure will be a big boy!
My daughter has an English Bull Mastif. Max is HUGE, but like you say...a gentle giant UNTIL someone "pisses" him off. I would take Max for a walk and if another dog even tried to approach, Max would let out this bark as if he was saying to "stay away". Dogs and people would not come near unless I told Max to sit and be still. Then others could approach.
I'm sure once the babies get bigger, he'll surely be the "big brother" and protect them.
I never liked big dogs either. I'm a cat person, but funny thing....when hubby retires, I told him he can have a dog and guess what I want him to get? A Great Dane! lol