What's the best way to store lots of kale to use for smoothies?
The party line from Still Tasty is to:


Cut out the stems, wash, and blanche for about 2 minutes
Dry
Store in freezer bags with as little air as possible


They indicate you will get about a year of storage from this method.



That being said, the method you propose is well known for herbs, and kale is certainly much heartier than an herb.  It should work very well, given that the application is a smoothie and you don't mind having the kale pureed already.  It should keep the kale usable for a year or so as well.

So the main issue with the traditional method is, are you willing to blanche your kale?  I know not everyone is.

If you use kale for other dishes and have to blend your daily smoothie anyway, you might use the standard method, and store it in daily sized batches, thus giving you the ability to use it for either a smoothie or some other dish.