For DQ, most of the games are free. There is a section for children where they are able to cash in tickets to get "prizes"....and for this section, you must pay extra....but I'm pretty sure you buy a "card" for $5 or $10 or other denomination. I don't remember needing any quarters for DQ. The prizes were decent enough to keep my DS's happy and we didn't mind spending the extra money.
For the resorts, they needed quarters.