I am floored at the idea that anyone would be offended to receive....
Decent people are never offended by other people's social faux pas -- instead, they gracefully overlook them.
But, that doesn't change the fact that the OP asked for advice about how to avoid the faux pas in the first place. The correct thing to do is for the guest-of-honor to write the notes and sign her name. If her husband wants to participate, she could mention that her husband loved the Yankee's baseball outfit, or he could send a separate note.