Wow, three gifts from Grandparents? I usually got one big box from my father's mother and some small gift from my mother's mother (she didn't have much money) and all that stopped when we got older. I think the whole idea of buying a bunch of "stuff" just to have gifts under the tree is silly. What's the point? As someone else said, they probably have all the little stuff they need so why not just do the exchange and spend more time enjoying each others company?
If you really feel you have to buy gifts, I like the idea of buying for poor children who won't get anything else that year. What a nice idea!