How about taking the "Behind the Seeds" tour at Epcot? It's an "up close and personal" view behind the "Living with the Land" exhibit, where you go through the greenhouses, learn about managed agriculture, etc. Haven't taken it but have always wanted to. Perhaps you could expand from the tour? Also, let the CM in charge of the tour know about your assignment...maybe there'll be extra info or help!
PS- I think the school system decision stinks. I understand the reasoning against taking kids out of classes, but as long as our local public school system teaches at levels several years below the actual grade, I'll continue to remove DD from school whenever I decide it's necessary. HONESTLY!!! Sixth grade homework was a worksheet on the correct usage of its, it's, which, witch, too, two, and to. DD had to correct TEACHER'S spelling/usage on the sheet- "sense" when she meant "since", using "loud" when the adverb (loudly) was the correct form, and THEN do the actual assignment!