Both kids use the Kidz Gear ones (found on Amazon). We use them in the house and on an airplane. Never in the car, so I am not sure about the headrests on car seats.
DD~6 years old~born June 6, 2008 (1st grade) DS~4 years old~born November 6, 2010 (1st year of preschool)
My son loves to wear headphones when he plays on the computer or when he plays his Nintendo DS.
Earbuds don't interfere with a carseat, but they can be uncomfortable after a while. Bigger headphones are more comfortable, but can bump up against a carseat. You might want to check the electronics section at Target or Radio Shack for one of the medium-sized pairs that have a foam cover but are still small and light.
Re: Headphones?
DS~4 years old~born November 6, 2010 (1st year of preschool)
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