My favorite restaurant in all of Disney! And lunch is a great idea - you'll still have daylight to enjoy the wildlife out th window!
Whle I always recommend making the ADR, I think you're very safe just showing up...especially that time of year.
We've made ADR's and then shown up 2 hours early and were seated. We've been going once or twice every trip since they opened - and I've never seen it full...so many people don't even know it's there!