If you plan to stay inside YNP you better make your reservations as soon as possible. Be came down from the Kalispel side after visiting Banff. If you want hookups Fishing Bridge is the main campground. We took Hwy 83 down it was quite scenic with many lakes.
I assume you don't plan to spend any time in Glacier. Once you get into YNP you will find plenty to occupy your time. The various geyser basins, Yellowstone canyon, the thermal features at Mammoth. And plenty more. Bear Tooth pass is not suitable for most RV's but you seem to know that.
If you run out of things to do at YNP there is always the Grand Tetons. Being from Canada I guess you may know what that means.... There is plenty to see there. And some like the Jackson tourist trap town.
We have spent at least a month in YNP and a week in GT and still haven't seen everything.
