I like option A. This is because the present perfect use here is appropriate since the past action has present significance...but also I think the juxtaposition of "Hell has frozen over," which is very colloquial and informal, with the later usage of the word "feast," which is quite formal and ceremonious sounding, is quite funny. I assume you are intending for it to be humorous. If you're not going for humor, I would switch out the second phrase for something that matches the informality of the first sentence, like "Let's eat."