I'm not very familiar with the rules for redeeming Savings Bonds. Can a bond owner endorse the bond and have a third party redeem it on their behalf by endorsing it as well?

No. The owner must be present to cash the bond. They can then give the cash to the third party, but the interest is reported under the SS# or TIN# of the bond owner. Circumstances where there is a power of attorney, deceased owner, request to transfer ownership, etc. are explained in the savings bond guides. This link will give you all the information you need to know on issuing and redeeming U.S. Savings Bonds.Treasury Direct

Thank you!