It is a noble thing you want to do, but the pop can tabs for charity was an unfortunate rumor. Ronald McDonald House will accept them, and thank you, because they figure people worked hard to collect the can tabs because of the rumour. However, they do NOT get more than scrap value for them. So, it would would be more worthy to just donate the little money the tabs are worth. A million pull tabs makes the charity about $366, or put another way, a hundred tabs makes them 3 and a half cents.
source: www.snopes.com/business/redeem/pulltabs.asp