With kids in sports, we found it was cheaper and easier to rent a car for road trips.
* use sites like Costco, Amex travel, Kayak.. etc to find the best deals.
* pickup/drop off at the airport is normally cheaper
* put that 'road trip smell' into a rental, not your family car.
* You can pick a car that best fits the trip (space = minivan, snowy = SUV, cheap mpg = 2 door spec).