I'd call this a must-see. We didn't see any whales but otherwise it was perfect.
We had a rental car, and easily found a parking space on the road. As advertised, the walk is a steady, moderate climb on a smooth, wide paved path. We saw a powered wheelchair at the top and there were plenty of strollers.
You get about ten different amazing views on the way.
There will, of course, be wind. I'll bet if you set up a team downwind you could run a business selling people their own lost hats.
There's no toilet facility here, but there is at Sandy Beach Park, just a tad before Makapuu as you come from Diamond Head.