As already noted, you will be able to catch an early bus to the AK.
I just want to warn you and others to NEVER try taking a taxi to the AK for meals or Safari or anything else before park opening. We tried this a few years ago and it was a disaster. The cab driver told us he tried taking another party earlier that week to the AK early and was not allowed in. For whatever reason, the AK gates do not open up for any vehicles other than Disney buses as early as the other parks.
One more warning....please do not ask any Cast Members about Disney transportation, especially the Front Desk people as they seem to know almost nothing about it. Ask away over here on these boards....and you can always trust the Disney bus drivers (the people in the purple pants) to give you accurate information.
