The prudent choice will be to refinish your ceiling first, the reason being that you won't be taking enough wood off of your floor to make that much dust. How do you know if it's thick enough? Well, I should hope it's still nearly a full inch thick, which is plenty thick enough. Don't waste your time and ruin the wood by trying to make it look like a dance floor. Sand it lightly and give it a couple of coats of tung oil.