Elizabeth Berg is an angel! I met her years ago and will never forget her kindness and warmth.
I do the same thing at our little library, never hurts to ask. We had NYT bestselling author Chloe Benjamin because she lived close by and loves libraries, no charge as well!
When I first started as a programming librarian I had a similar situation. I saw that Molly Ringwald had a book coming out of short stories. I tweeted her publicist that we would love to host her. The tour was full ... but then a week later there was a cancellation and we got that slot! It was so amazing to host Molly. We now host authors on tour regularly, but the serendipity of having Molly Ringwald at the library is one I will never forget. I am with you on this ... never hurts to ask and I always do as you just never know. Also, it won't let me delete the previous post that went up when I hit send by accident. sigh.
I deleted it for you, Janebrarian :-)