While Lynn Canyon is located at the base of Seymour, you'd have to go hiking through the forest to experience any sort of view at Seymour - definitely not doable at night or at dusk.
I'd opt for Cypress instead. The reason for this is that there is a fantastic look-out point half way up Cypress with a parking lot and picnic tables. It's the same place where I took this photo:
The drive is relatively short from Lynn Canyon and it's safe to do at night. There is a turn-off from the highway that you take to get up to Cypress and this lookout. Note that this road, while paved and safe, is not lit, so be cautious at night.