It's pronounced keɪ (from your link - The spelling quay, first appearing in the sixteenth century, follows modern French. As noted by the Oxford English Dictionary, third edition, the expected outcome of Middle English keye would be /keɪ/ in Modern English). Or key (with modern spelling).
We actually originally pronounced it as "kway" (the American pronunciation we had heard) but then had a saying we'd tell customers (when asked) of "pronounce it however you please, so long as you're happy using it!" :)
