Okay, so I now realize that my earlier speed projectioin was a little high, I completely forgot about the weight. I am planning to go atleast 80 kilometres a day increasing to 100 as the trip progresses. In reference to the Glacier Park, there is another route from Baynes Lake, west of the Park which I could take as it could be closed.
Are you talking about coming down PR 93, crossing at Roosville and heading south through Eureka to Whitefish? If so, you will probably hit cold/wet weather if you start your trip in April. I have ridden the stretch between Eureka and Whitefish three times. The first two times ('99, '00, north to south) were cool and wet in the second week of June. In '09 (south to north) I got rain and it was still a bit on the chilly side in the third week of June. Circled through Canada--Sparwood, Pincher Creek and Waterton Village. Except for Eureka to Sparwood, which was nice, we had rain at some point the other days. Picher Creek to Waterton was downright wintry, with snow falling on the mountains. Again, this was in the third week of June. And Logan Pass in Glacier was still closed when we got to St. Mary.
I would definitely start later if at all possible.