First, congrats on the long drives with your little ones!
We've had many deep discussions on most things. I just keep it age appropriate. The car seems to be the place it happens the most.
When my kids were younger I played kiddy music and they liked it but they went through phases of what they liked. At age 3 they like Pearl Jam. By age 4 they liked Cheap Trick. After that I played what I liked. But I did play slower music or softer music to calm them more. They wilder the music the wilder they got. Same with TV shows. Slow paced shows kept them not as wild.
2 of my triplets must have their bunnies from when they were infants. They're 7 now and they cannot sleep until they have "bunny" with them. And we take them on trips and I have to make those top priorities of things not to lose or they will cry and be very upset. These are things that soothed them as babies when mom couldn't spread herself out enough with 3 babies at once. So these are important for the two. and they are the two more independent and self assured of the three.
K. B
mom to 5 including triplets