Yes, you can upgrade. The following are the prices for the plans. If you are going from QSDP to
DDP the adult price difference would be 18.01/night (assuming this is non-peak season). But here are the numbers so you can do the math yourself. You can always just call Disney and they will quote you the price difference.
Quick-Service Dining Plan (2 quick service, 1 snack per night)
(price for full year)
$37.58 per night ages 10 and up ($2.59 increase per night over 2012)
$14.32 per night age 3 to 9 ($2.33 increase per night over 2012)
Regular Dining Plan (1 table service, 1 quick service, 1 snack per night)
(non-peak)
$55.59 per night ages 10 and up ($4.05 increase per night over 2012)
$17.16 per night age 3 to 9 ($2.17 increase per night over 2012)
(Peak Season)
$56.94 per night ages 10 and up ($3.40 increase per night over 2012)
$18.16 per night ages 3 to 9 ($2.14 increase per night over 2012)
Deluxe Dining Plan (3 meals - either table or quick service - and 2 snacks per night)
(non-peak)
$99.97 per night ages 10 and up ($14.45 increase per night over 2012)
$26.84 per night ages 3 to 9 ($3.05) increase per night over 2012)
(Peak Season)
$102.27 per night ages 10 and up ($12.75 increase per night over 2012)
$28.91 per night ages 3 to 9 ($3.12 increase per night over 2012)
Peak Season Dates:
February 14 23, 2013
March 8 April 6, 2013
May 31 August 3, 2013
December 13 31, 2013