What a great idea!

I think first thing - you might need to get some sort of a special bank account set up. You might need a trustee or someone to oversee the account. A bank manager should be able to help you or point you to someone who can advise you.

People that donate will want to know that it is real and not just an open account that might be used for general expenses.

There have been scams done that people just ask make up a story and ask for money and it is not legitimate.
That's why you need to have it set up properly and there might even be some sort of legal status involved. Not sure about that though.

I know a few times when local kids have had cancer there is a donation jar in our local store, or they sell wrist bands,car washes, raffles of donated items from merchants {tax write off for them}.

Oh and after you get the account in place contact your local news station- they usually will do a short story on things like this and that gives a plug for your charity/donation site.