Not sure why arriving to and departing Haines is of value both ways, unless you're trying to avoid going through Canada Customs. But then Haines wouldn't be the correct choice as the majority of the Haines Road is in Canada, and from there the Alaska Highway to the border at Beaver Creek & Port Alcan (US Customs).
The AK Hwy around Beaver Creek is one of the worst stretches of highway in the north. One hundred miles might take about four hours, especially if you are towing.
There will be extra ferry costs for taking your toad. Cost is calculated by the number of feet in length your rig is. The AK ferry isn't the most cost-effective method of travel and adding in the cost of your toad will make it more expensive. It is less costly to drive and buy fuel.
Many campgrounds in Alaska close immediately after Labor Day. The owners often head south themselves. Same in Yukon ... a few stay open but not many. The tourist attractions often also close after Labor Day. Fuel isn't usually an issue as we drive vehicles here and need fuel to burn.
