That I am not sure of it seems a little unethical that you didn't (I am assuming) limit your campaign to those countries you could ship to rather than the whole world.
Shipping of batteries I am assuming you are talking Lithuim type batteries? normal alkaline batteries wouldn't be affected I think even lithuim can be shipped potentially. Here is a UPS document from the UK I assume US would be similar that may help you.
https://www.ups.com/assets/resources/me ... teries.pdfOne thing to note, potentially those worldwide clients get you across the line of funded, and then if you refund them you wouldn't have reached goal..
In any case you will be refunding them in full whilst KS will retain their commission from the sale so effectively you will be refunding approx. 110% of their pledge which now ends up costing you more than their pledge value..