Just my personal opinion: dogs are pets and should not be confined to kennels or crates. They deserve freedom of movement. How would humans feel if they were confined to a crate by another more powerful being?
I would suggest getting a very large dog bed (or two or three large sun-lounger covers) for the mother and puppies to sleep on. The issue of the temporary protective instinct of the mother has already been discussed in another thread; this instinctive protectiveness will rapidly pass as the puppies grow.