I get mine at Target as well. We save our coin, roll it, then split it three ways (between our children). Once we had $150 I got them each a gift card there-now they can use it to pick their own souvenirs.
I know our local private school participates in the Scripts Program (a percentage of the sale of a gift card goes to the school). They can order Disney cards in higher denominations. The school keeps 2% of the sale. Do you have something like that in one of your local schools?