Is this a good Idea??

I dont think its a good idea. Since shes just dropping it off she might not get any money in return. And a lot of people would be hesitate to believe that the money would actually be going to charity. Maybe she should think of another idea.

I don't think it'll work unless she knows the people and they feel obliged to help her. There was another idea that was similar to this. It's called the $10 project. Each person is given $10 with no conditions attached, apart from the fact that they should make this money earn more money. And the profits should go to charity. Some people made a huge sum with this capital but some people just kept the $10 as pure profit. I guess some ideas need to be worked out through a trusted circle of friends first, unless your cousin thinks the number of people who will drop off $4 are more than those who will ignore it.

its a cool way to riase funds for charity but im sure not everybody will send her money.

Well I think it won't be effective. It's better to put a flier to inform that your cousin will be selling gifts for charity. For anyone who want to participate, they can put a Christmas sock or a red color fabric at their mailbox as a sign. Then your cousin may visit the marked houses to sell the gifts.