You'll walk and walk and walk. Weather during Mardi Gras usually varies from 30-90 degrees fahrenheit, so come prepared. Just make sure that whatever you wear you can take off if you need to, or put more on for warmth. Bring disposable pre-moistened towelettes. Your hands will get dirty and its hard to find a sink on Mardi Gras.
Some people pack an ice chest and use a wagon to haul it around.
Only do this if you are staying outside of the Quarter to watch the parades. There are too many people in the Quarter to haul a wagon through. It is literally shoulder to shoulder for blocks. A disposable camera or two is your best bet. It is well worth the money to avoid the discomfort of not having a place to relieve yourself.