Well, usually the dates (seasonal-based) give the first month of the season to design and the second month of the season to judge. I often also shift it a day here or there, to better align with weekends and such-like.
For Fall 2009, that would be:
Announcement of "Official" Start - Monday, Sept 21, 2009
(only relevant when a design restriction applies, which is not for Fall... though I *still* want to do something with pink)
Deadline for Submissions - Monday, Oct 26, 2009
Deadline for Judging - Monday, Nov 23, 2009
Announcement of Scores and Ranks - Tuesday, Nov 24, 2009
Just in time for Thanksgiving. :)
And therefore, our not having a design restriction means that you can have them buy whatever they can afford. Given the progression of game development on the wiki (http://icehousegames.org/wiki/index.php?title=What_Can_I_Play%3F
), I wouldn't advise anyone to get only one of each set (Rainbow and Xeno) as one can play far more games by buying the same set spectrum until one has five of them (i.e. 5 monochrome stashes of 15 matching mids) and then complete a collection with five full sets of the other spectrum (and a gray stash and a pink Treehouse).
Of course, you can better determine what is a reasonable expense for your kids than any of us.
Some other, random (unsolicited) advice:
Buy Bulk - If you buy 10+ sets at a time, you get them for 20% off:
Encourage Sharing - If every kid had, say, two sets; and they are encouraged to work in teams of two or three (or can be assured of being able to use another student's set[s] during testing and final play for judging) then the sky's the limit! They could design for monochrome stassxhes OR Treehouse sets. On that note:
Don't Forget Xeno - Some folks might prefer its ethereal quality over Rainbow's brash hues, but that could put a wrinkle into group buying (i.e. if only a couple folks want Xeno). BUT, you get a great bennie--folks can design games using more than five colors (although maybe not more than five STASHES, which is a LOT of mids). Of course, the Looneys are really cool folks, and they might be able to mix-and-match and still offer the bulk price (I dunno).
Other Equipment - I concur with M. Myers: try to avoid significant investment in other play equipment, if only because that will over-emphasize or -encourage the use of said equipment, to the detriment of diversity. So don't "require" that they have dice, or a particular board, or anything.
Experience - I'm starting to stray from consumer advice to pedagogical, so forgive me in advance. That said, it might be beneficial for the class to play a large variety of games--fast and loose, just to see the design space's boundaries and options--before they settle in to their own designs. This sort of relates to the equipment thing: if they play a lot of games that use chess boards, guess what they'll try to design? Or if they play a lot of games that use no board and use the inherent shape and dimensions of the mids, guess what they'll design? But if they play one of each general type of game--minis, chess board, arbitrary board, other-shape board, high randomness, low randomness, dexterity, logic--they they'll realize how versatile the mids are, by virtue of the number of their intrinsic properties. That should lead to a much wider design space, befitting an open design competition.
Hope this helps;