Frank,
August should be a good time to see Denali and the Dempster.
The old denali highway is a good road. In the late afternoon on the large willow flats watch for moose in the willows. Lots of camping spots.
The dempster is a good road though all gravel. Make sure you have good tires, with the heaviest load range is best.
The only services on the highway are at Eagle plains about half way. Camp wherever you want. There is a campground at Toombstone and another creek that escapes my memory right now. the scenery really changes once you climb up past the Toombstone campsite. There is a new visitor centre at toombstone.
You should be able to see some caribou further up north of the arctic circle. Have a good set of binnoculars.
If you need a shower or do laundry etc give us a call. Send me a PM, if you want.
robbie