Bless you for your efforts in helping these wonderful little creatures <3
I would call both the airline and airport to ask about their rules and regulations on bringing them with you.
Not sure but since california isn't your final destination it wouldn't be a huge issue?
Air travel is tricky though, especially now, idk if it's a possibility to look at having a flight that goes to vancouver then to seattle?
I've also been curious about what traveling across borders with them would be like in regards to policies in place. Do they need updated vet documents within a certain time frame?
I know things greatly differ between modes of transportation also, and air is the most strict. (I live on the bc/washington border and used to travel back and forth once a week via boat quite easily before 2020)