You are happy with the X3, sans the sunroof functioning properly. It seems like you are looking at purchasing a new one for the sake of insurance.
My recommendation would be to keep it; however, put what would be your new monthly payment aside in a separate account for funding your next car when you become unhappy with it. Draw from this account when you need to repair the X3 or renting a car to get to your parents if you feel uncomfortable driving your X3 that far. After some duration, fix the sunroof. Close the account when you are no longer satisfied with the X3 and use the remaining funds towards to the purchase of the next car.
Iíve only been involved in two incidents in my life where unexpected mechanical failure didnít allow me to get to my destination: 1) heater coil failure in an older vehicle 2) Electrical issue with three month old vehicle.
I wouldnít justify a new car based on a child. Kids were born on the Oregon Trail, well before the advances of cellphones and 911. Kids are a lot tougher than we all think.
But if you want a new X3, thatís a different story and you should go for it.