I drove from downtown San Francisco to Oakhurst (nice small town and my hotel base for Yosemite) in about 4 1/2 hours. I left at 10:30 in the morning and had no traffic problems anywhere.

With regard to avios - have you fully explored the sign up bonuses for the BA AMEX cards and the AMEX Gold cards? It seems to me that you could generate at least 50,000 to 90,000 avios between you and your wife in about 4 months if you aggressively pursue this. Apologies if you are already enrolled in these.

However doing this leaves little time left for ensuring seat availability.