A poster had mentioned whether this would be solo or crewed, and I am thinking a crew of 2-3 people including myself.
My advice then would be to choose crew members that are sailors with as much offshore and circumnavagation expeirence as possible.
I would also advise you to get some experience on a short trip just to get an idea of what it is you are suggesting, and possibly reconsider.
I'm not going to knock you for having something that you feel strongly about and wanting to do something that helps others, but you seem to come across as not having a realistic idea of what it is you are getting into. That will tend to generate quite a bit of critisim here.
I do wish you the best of luck in your endevour to help sick children, and I hope you don't kill yourself.
If you choose to continue, and provide more details with more specific questions, you will find that you get more useful advice.