If you are actually going to Indianapolis for this event, give yourself A LOT of time to get there. Pad your trip with extra days in between things for sure! My DH went to the last race of the season in Homestead, Florida. It took him HOURS to go from the highway exit to the parking lot. It was so big and congested that he never wants to do it again.
These events are tremendously popular.

About flights, There are no direct flights from Vancouver, and there are none for sure from Seattle. But if you come to Seattle you're 15 minutes from my house!
The flights from Seattle to Indy are a lot cheaper than the ones from Vancouver too.

I hope that helps.