Low income family needs a new car

My family has a mini van that has high mileage and is getting to expensive to maintain.

I need to replace it with a new car.

I have 2 kids that have disabilities.
My son has autism and has lots of appointments.
My daughter has epilepsy among other things.

The car im funding for would be used to go to thier moms house, therapy appointments, grandparents 1 of which live outside the city, shopping.
My bottom amount im funding for is $12,000 for a car with half the kilometers my van has.

If i can raise more then i could get a low kilometer car.
My family needs a midsize car.
Please give what you can.
Thanks