I´d agree booking a fully refundable rate for your dates would be a good idea especially as you´re not flexible date-wise.
I doubt GRGD will be offered for these properties for June as it´s definitely not low season, plus GRGD are NOT upgradable (if you have status)
I´ve sometimes seen promos for the summer roughly 3-4months in advance, I´d closely watch the Fairmont website as well as third party sites like Expedia etc.
In my opinion any rate <$200/night is a good deal, and the best deals for the summer I´ve seen over the years have been in the $150/night range (but definitely not offered consistently), just to give you a rough idea...