2 fantastic things for car rides with little kids: a roll of scotch tape, and a box of band-aids. Your car will be a mess, but just let them go to town. Opening, peeling, sticking, they love it!
I always keep a jar of bubble mixture in the front and on long trips use it with the air conditioning. They blow to the back of the car and can cheer anyone up! Even babies!
Love yhe fart noise option. We keep colors in a crayon roll, pages of their favorite characters an if we are feeling very brave, play-dough.
We also like to play the rhyming game: One person picks a word, then everyone takes turns (or just shouts out) words that rhyme. Another recent game we have played is the numbers game. It started out as a way to get away from the rhyming game...To my daughter I asked, "If I had 2 horses, and you had 3 horses, how many horses would be have together?" Turns out she loves numbers! She even liked having a turn where she creates the word problem. Subtraction was a little harder for her, but still pretty fun.Oh, and audio books. Not sure if we could survive without Jack and Annie (The Magic Tree House Series).