Hwy 97 up through the Frazer River Canyon is amazing. North of Cache Ck., BC, the road is less entertaining, but the scenery is amazing and there's lots of neat places to stop and check out. Most folks want to start out an Alcan adventure from Milepost 0 at Dawson Creek, but there is an alternate route that is well worth considering. From Chetwynd, take the the Hudson's Hope cutoff. It goes for about 80 miles through some fantastic road and scenery. It comes out on the Alaska Hwy at Ft. St. John. A couple miles north of it, actually. About halfway you can take a short side trip to the purported world's largest earthen dam. Can't recall the name of it. Ft. St. John is a fairly modern town with all the amenities, including a Wal-Mart, so you can stock up on whatever it is you need or think you will need. They have some decent hotels, too.
I have only done the Cassiar Hwy once and that was in 1981 in a car. The first 100 miles were paved as was the last 80 miles. Everything else in between was gravel and quite rough in places. Still, it's a very scenic route and if one intends on riding the highway both ways, it would be worth considering taking the Cassiar at least one way.
On the Alaska Hwy, there are few town and darned few communities, most of which seem to center around some sort of lodge or construction camp. One notable place is Toad River Lodge. I can't speak for the lodging, but they serve up a terrific breakfast. And don't expect too much at Watson Lake. They have a couple motels there, but they're definitely not 4-star! At least there are a couple garages and auto parts stores there, as well as gasoline. Just to the north where the Cassiar Hwy intersects, there is a pretty nice restaurant with gas pumps.
Whitehorse is a great placed to stop and spend a day. Everything is there for one's convenience--fuel, lodging, good restaurants, stores and shops. You can even take a paddle boat trip on the Yukon River. I believe on option is to do the dinner cruise on the boat.
There's nothing of note between Whitehorse and Haines Jct, but they have at least one decent motel and a couple gas stations. Don't know about restaruants, but you can gets snacks and drinks at the gas stations. A lot stuff between Haines Jct and the border is closed, I suppose due to the economy, so gas up at Haines Jct. The most expensive gas is at Beaver Creek, but there are a coupe motels and restaurants there. It's about 180 miles from Haines Jct. to the border and just a couple more miles to your first gas station. You should be able lto make it on a tank of gas so you don't have to pay so much for it at Beaver Creek.
To back up a tad, the road is boring between Ft. St. John and Ft. Nelson, however Ft. Nelson is fairly progressive and there is a pretty good RV park and campground at the north end of town. There's another neat little campground/RV park about 60 miles or so to the north of there. They have a good restaurant and they make their own bread there, fresh daily. I don't recall the name of it, but it's on the left side of the road as you're heading north.
So much for the travelogue. Hope this helps. Oh yes, depending on what time of the year you go up, you should expect to run into some road repairs going on. Hopefully you will be pleasantly surprised as we were last year and the year before. No road construction.