Welcome to cruise-chat!
I am known as a straight-shooter in my advice. You need to change your flight times. You are assuming everything will be on-time with the flights and that there will be no glitches or delays. One little problem could mess you up.
And since you need to pay the price to rebook, you may as well rebook for the day before the cruise and get a hotel room. This is what we "cruise pros" do.
Flying down a day early means flight delays generally won't be a problem. It also means that if luggage was lost it more than likely will be found and delivered to you before the ship leaves. And it also means you only need take a short ride to the pier from the hotel and arrive for your cruise rested and refreshed instead of rushed and frustrated.