We don't have humidity issues here in CA, we're actually in a severe drought - so drying should be fine, if anything it would be too fast. With a high grog content on other porosity added to the clay body, the pieces will dry out even better at the core where it's most important.
The piece will be a big relief that starts with a base around 3-4" thick. It will likely get both carved and added to. Piece will get cut up and put on boards (or will already be cut into tiles beforehand) and then onto ware carts for drying. Whole cart will be under a plastic sheet to slow it down. Anything not fitting on the carts I'm going to have to rig up some sort of elevation system to get airflow under the work like Marcia mentioned with the sticks, only with multiple levels due to volume of work and because many carts will be occupied with student work. I don't like to push force drying too fast, but bringing the carts into the heated building will help, as will force drying in the kiln if need be. It'll likely take a month for the work to dry enough for firing is my guess.
Firing will be in downdraft gas kilns, fired over the period of perhaps a week and cooled over several days as well. With the thickness, it will likely need down-firing to keep from cracking in cooling. Individual pieces will be flat on the backside, so they will all get propped up on balls of kiln wadding (equal parts silica grog kaolin) when placed in the kiln.
This has all happened really fast and I dunno who's idea it was to at the last minute decide to have this huge ceramic piece/demo as part of the event. This is not really one of those things you take a last minute approach like this, but we're doing it. If anything, this will be a big, fun experiment with tons of clay! It will get lots of documentation, no worries there