I'd echo what the others have said about the emotional aspect of the trip, so I would give priority to packing what makes you feel "good" about yourself. Who says that you can't clean or sort in a nice outfit? Borrow old clothes from your parents for the really dirty jobs.
You may find that the business type of meetings take longer and are more draining that you think. You may find that you have to act as your parents advocate and in dealing with not- too-helpful bankers, doctors etc, if you feel confident and pulled together, you have more energy to push for what you know is right for your parents. Good Luck!