We use gift cards instead of cash. We stockpile them for a few months before our trips (our kids' school sells them as a fundraiser) and just buy a few at a time up until we leave. Then we can just hand the kids each a card to use for fun money each day and it's not a big deal. We never spend cash in the parks unless I"m getting a funnel cake!!
Do cart vendors and/or CS accept Disney gift cards?