For travel packages at the Disney site online: You actually do put $200 down as a deposit, or more than that if you choose. Then, you can pay it off in installments and your payments will show up online. They don't really mind how you choose to pay it off, little by little or all at once, as long as you pay it off by the date they assign, I believe it's 21 days before travel or something like that.
For room only, I don't think you can pay it until arrival.
Last trip: Dolphin, March 2013
Past Stays: Contemporary, Grand Floridian, Polynesian, Beach Club, POP, POR, Dolphin
1990 August Honeymoon - Grand Floridian
Delighted Disney Return Guest since 1981