according to my notes, there are change machines (quarters) at the following places:
mk: under the MS railroad, f. shooting gallery, tomorrowland power and light, splash m. gift shop
epcot: living seas gift shop, the land near garden grill
ak: inside rain forest cafe (takes $5 and under bills)
HS: pizza planet arcade(who knows if it will be there after reopening), mickeys of hollywood, TOT, prop shop
DS: inside rainforest cafe ($5 and under bills only)
Your mileage may vary. pennies can be had at most retail locations provided you don't ask for a lot. personally, i'm bringing all our change pre stacked in decorated m&m tubes.