Can you not just call the Best Western and tell them you'd like to cxl your reservation? This trip is still over a month and a half away.

If you skip Napa just stay in San Francisco on your arrival day and do what you were originally planning on doing on Day 3.

Day 4 (as originally planned) - Skip Hearst Castle, that will save you about 2 hours right there.

Day 5 (as originally planned) - You will be contending with some of the worst possible LA traffic, I'd skip Hollywood and stick to the coastal sights like Venice Beach and Pine Ave. in Long Beach. Detour through the South Bay cities like Redondo Beach and Hermosa Beach instead on the way to Long Beach.

If you skip Napa and have an extra day, I would find a hotel in the Santa Monica area and have an extra day to explore LA.