Have goofy with ALL of the things that make him gain MP faster (MP rage, MP haste, etc) and MP Gift. Have dodge roll and ars arcanum on Sora. Just dodge roll around until you have a clear shot then run up to whichever one you're concentrating on first, and use ars arcanum. Repeat until one of them is dead, then just kill the other one normally. Goofy should keep you with ample MP with MP gift.