One other note -- there are often ways you can mitigate anything you are worried may be a problem.
Lots of kids - stay away from kid friendly zones, set good example with your own kids as applicable, don't be afraid to report infractions or issues you see.
Deck chairs - get up early, get a primo spot (just don't hog it all day). Look around the ship for those places that are partially shaded or just not near the main pool and you'd be surprised of the room you find.
Granted, I've not been on the Legend, but I read similar bad reviews about some ships I've been on and didn't find those issues to be a problem - having a positive attitude will help as well.