Your ideas sound great!
For me- 6+ hours on backroads each way!!
...yeah...( I2+ if I ride from Montana...)
Area looks to be a mix of environments, from desert plains to rolling hills? input Mike? Google maps shows it to be like the Spokane area. Hot time of the year, so pack accordingly!
Personally I would ride down Thursday, and have to leave Saturday morning being the end of my vacation 'cause I need a day to recover from being away from home for 2weeks!!
I will continue to "nibble" while this meet develops!