I started DS (7) saving all the change he could find about a month ago, told him that before our trip in late September we would exchange for bills and that could be his spending money, also this is a good way of teaching you child to count money and add (great project for homeschoolers), every piece of change he finds he adds to his total, so far he has about $20.00 but that's only three weeks of savings, by the end of September he'll have probably at least $100.00 and I won't have to worry about saying "no, you can't have that" as he'll have complete control over his own money.
I too use a debit card all the time but am making myself use some cash so DS can continue his savings.