We were also on the Radiance, but May of 2005, and it was an amazing experience. Radiance has self balancing pool tables, and our boys loved it. We live in Tampa, and the airfare to Vancouver was double compared to flying into Seattle, so we decided to leave a day early, rent a car in Seattle, and drive to Vancouver. We spent the night in Vancouver, and so we enjoyed the sights in both Seattle and Vancouver. On the return, we booked a shuttle to drive us back to Seattle. I had to convince my husband to go because he doesn't like cold weather, and after almost two years, he still talks about it, and we're hoping to go back. Dress in layers and it will help with the change of temperature. And if you can, try to get a balcony...while you're in the glaciers, you will have the best view. We went in May, and didn't see much of the wildlife. We did the helicopter/trekking at Mendenhall Glacier, and it was amazing. We booked a horseback ride in the Yukon Territory, and it was also a great experience. They took us along Emerald Lake, and then walk up the top of what looked to me to a small mountain where the view was just breathtaking.
Book early, and hope that others can help with the best month. You will love it.