I didn't do my normal search due to the pressure of time for a stay Nov 29-Dec 1.
I repaid $70 (a night) for Hotel la Fortuna with a view of the volcano. This was through the agency known as Anywhere. I saw the hotel first on this page:
http://www.arenal.net/arenal_volcano_national_park.htm
I don't know if Anywhere allows one to move to another hotel so if not I hope this hotel will suffice. The reviews on TripAdvisor are mostly positive. I just regret not doing more research but the price point and location are a good fit.
Does anyone know if you need to prebook activities like the Toro SkyTrek and Arenal white-water rafting?