With the obvious exception of not being able to get things like luggage tags for making use of "Magical Express", I believe you could call and make a reservation for today.
The only down side is that the time of year you're talking about going, Disney usually has special discounts going because it's off season. However, the deadline for making reservations with the discount could be weeks to months before your expected travel dates.
As an example, last year, Disney offers a special deal for dates between 01/01/2006 and 02/18/2006. But to take advanage of the deal, you had to book by 12/18/2005. And the most resent example was pretty much the exact same deal for available dates between 10/01/2006 and 12/16/2006, but you had to book no later than 09/30/2006.
And here's an even more applicable example for the OP. Currently "Disney is offering discounted vacation packages for stays 1/1/07-3/8/07 (1/12/07-1/14/07 may be blacked out). The packages include discounted accommodations and Magic Your Way tickets, plus FREE Park Hopper and Water Park Fun & More ticket upgrades." (quoated from
www.mousesavers.com). But to take advantage of the offer, you must book by 12/16/2006.