Plenty of shade on the beach at CN .... Lots of trees (no umbrellas). Never had a problem finding shade without "marking your territory" at first light. If you want an umbrella at the pool, though, those are a little harder to come by but there are also large palm trees around the pool that offer shade.
We have been to CN in summer and in April at almost full capacity and we have never had a problem finding a shady spot on the beach. Lots of trees - so lots of shade - just move your chair to the sahdy spot. That is probably the key - they have lots of chairs so you can move them to make it convenient for you!
Two weeks ago I'd run the beach before 6, and there was practically no one there at all. Maybe a watersports guy or two cleaning off the chairs and a groundskeeper raking the sand.
I saw one spot with "stuff" on it to claim the chairs one day, but in a beach that long and wide, unless you need that particular location, you'll have no issues.
By 8AM there were 15-20 people on the beach; still plenty of room.
I spend my week on the beach so I can't speak for the pool but
I've never had a problem with finding shade or a beach chair at CN. There is always a tree available for shade on the beach and there always seems to be an abundance of beach chairs and floaties.