First, even if you were not going into surgery, you should have a Will. Accidents can happen to anyone, at any time.
Second, in a Will you can NOMINATE a guardian of your minor children, especially if there is no surviving spouse. The probate court would then USUALLY confirm that -- it does not have to, and might not if, say, the person you selected was not suitable in the eyes of the court, or the children strongly objected, or other relatives -- such as grandparents -- strongly objected.
A form Will is available under Forms at
http://FreeAdvice.com - one is free, some are state specific and cost a few dollars. You should ask a lawyer's advice, and make sure the Will is properly witnessed.
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