I think you should try to get a spot just inside the BC border ( 14 minute drive from Jasper ) called Lucerne, it's right on Yellowhead lake, the camping spots are priced much more competitively; and you will be located right in between Mount Robson Provincial Park and Jasper National Park..... It's Beautiful !
I've camped all over the parks, this is by far my favourite spot.
Provincial Park Site
Lucerne Site
ps...
When you get to the Jasper Park Gate, and the attendant asks you if you will be visiting the park tell the no; you'll be driving though to BC... this will save you 20-somthing dollars for a park pass.... seems you will not be staying in the park, you do not require a pass; that saved money will more than pay for your extra 14 minute drive and campsite for the evening :-)