Hi.
I did the trio in June w my adult daughter a dog and a cat!
This is what I found;
It is better for animal to use the tunnel as then you are in the car with them. If thry have to go in the car in the ferry it rocks more than above n many people disregard the instructions to disarm the car alarms so they are going off too. Very stressful for animals.
I did all the driving. Left nice n early. They barely look at pet passports going out.
Use the toll roads. What you may save in tolls you will spend on fuel.
I stayed more along the coastline and stopped iver at a prebooked good hotel for the night at the border. The pets are a few € more on room charge.
Got moving before 10am and drove down to San Juan de los Terreros, arriving late afternoon.
Not stressed.
Would do it again as the pets hate flying.
Hope this was helpful
Jenny