Okay, how about estimating what you'll spend on food - and purchase a Disney Gift Card in that amount/vicinity?
JUST for example (your calculations will differ):
Four people, seven full days (six nights)
$2.50 per snack times three snack per day pp = $210
$8 per CS times two meals per day = $448
$30 per TS meal times two meals = $240
Total = $898
Just for the record - the Dining Plan for four adults for six nights would cost $936. Now, granted, you can't swap TS credits for CS credits - but you could eat at relatively quick sit-down places like Plaza Restaurant, or um, Beaches & Cream.