Update: TransferWise worked out great. I would certainly use this again and would recommend it.
Total cost to me was about US$8 (!) and it went through in less than one business day. Easy to set up, you can even pay with a credit card (for a fee). Cheap, quick, easy - hey, I like those.
As a comparison, I attempted to do the transfer on Saturday from my local credit union, a good CU for most things, but they totally failed at this. First I called their branch in advance before going there to ensure I had all the info I needed. Staff person there assured me the info I had was all I would need. I went in, they then demanded about 5 additional details about the recipient (the street address of their bank, for example) which I did not have. They were also going to charge me $50 for the transfer, couldn't promise what exchange rate they would use, and would impose a surcharge for taking dollars out of my account and converting to Euros before sending them. I was estimating the cost in the neighborhood of $70 (from a credit union). And it would take 5-7 business days.
Yes, I am well aware of the risks of pre-paying for any accommodation, I considered those risks and feel OK about it in this case. To answer questions: this is a small B&B/Pensione in a city on Sardinia (Italy). The B&B is in a 17th century building, deep in the city's old town and high up in that historic quarter, where there are only a few places to stay. It looks a little funky (hey, at 300 years old, we all are) and quite charming. Prices are reasonable, but not totally-crazy-too-good-to-be-true. I found it online using a big-name booking service. I see a hundred reviews (generally very positive) across a half-dozen different booking sites from the US and Europe. I am not naive about online reviews and I think I can usually spot fake news. If this turns out to be a scam, they've worked very hard and have done a good job. Anyway, I'm confident the place and the recipient are legit. And worst case, if we do get scammed, it's not a huge amount of money (3 nights at a fairly inexpensive place).
Bottom line to anyone who stumbles across this thread in the future: TransferWise worked great for me. I'd use it again in the future (but yes, always be careful before sending money to anyone). Hope this helps someone down the road. Cheers.