For all the other parades other than Zulu, set up in the general viscinity of Fat Harry's
http://www.nola.com/bourbocam/other_media/about_paradecam.ssfWithin two blocks of this location, there is a church that offers CLEAN port-o-johns for $1. The funds go to the church youth group and the kids actually clean the pots and spray them down between uses. As you're leavign they give you a hand wipe or a squirt of anti-bacterial hand lotion. The best spend dollar at mardi gras. I'll try to find the exact location and repost but getting in this general area should be good. Lots of families in that area set up with their kids up on ladders.
Most of the parades pass this point but Zulu and Endymion do not. For Zulu you could set up in the general area of Jackson and St. Charles (where the parade turns). There are a limited few establishments in this area that provide drinks and restrooms. You'll usually have to buy a drink to get into the restrooms.
This is also an option -->
http://www.sneakyleaker.com/ ;)
also bring an ice chest. buying alcohol at the bars takes forever. You could miss a quarter of the parade while waiting to be served.