Holiday Inn on King Street is probably the closest. But you'll be fine anywhere downtown with easy access to transit. Easiest way to the course from downtown is to take the King streetcar west to Jamison. From there it's just a couple blocks south to a footbridge over the Gardiner/Lakeshore Blvd. The course is right there.
The Argonaut Club is just west of the course and they've got a map on their website:
http://www.argonautrowingclub.com/directions