Message behind this parable of Jesus?

I believe the first two you wrote are accurate morals to glean from this parable. I also think the 3rd one is that the ones who said "Yes", but didn't obey were representative of the Sanhedrin, because they were supposed to be the ones who were the "keepers of God's Word", but they didn't keep it themselves, and the ones who said "No", but later obeyed are representative of the Jewish people (and Gentiles) who were unrighteous but were willing to open their hearts to the Lord.