What shall I do about my dad?

In this life, you only get one set of biological parents. I think you should definitely make time to visit your dad. Let him know that you have something very important to do, but make sure you see him sometime in this holiday season. Preferably, I think you should go and see him for Christmas then make time for the important stuff later, but if you have to absolutely get this "revise" thing done then do. Remember, these are the holidays so don't be a SCROOGE! Good Luck!