I did a similar trip awhile ago and we did Vancouver for a few days without a car and then rented from a cheaper non-airport location for pickup the day we were leaving. No need for a car in the city itself or when seeing some things in the area (like the Capilano suspension bridge).

I’d second skipping Calgary. Nothing against the city but doesn’t seem worth it given where you’re flying.

I’d also consider skipping Jasper and staying in Banff/Lake Louise area and doing the bus trip to Columbia Ice Fields. This is much more subjective but it saves some driving and I think you have enough good stuff to see already. Depends on the type of traveller you and your family are though. You can also do Kamloops one way of your drive and Kelowna the other to mix it up a bit.