Paying for future trips while in WDW?

[hAm53]

we'll be headed to WDW in a couple weeks for our wedding planning session, and have acquired about 600 bucks in Disney Dollars from when we've gone to the mall, birthdays, etc. since we only have $110 left to pay on our planning trip, can we bring the rest of the disney dollars with us and pay for our wedding hotel (you need to have that booked when they book the wedding a year out). we have about $1000 left to pay on the poly part of our trip (after what we figure AP discounts will give us a year from now), and was hoping to get that amount some.
can i just walk up to any guest service counter with our september '05 reservation number and hand them the rest of the disney dollars? or can you not pay for future trips in advance?
thanks!