If you are selected for Summer Seminar you will receive instructions on how to arrange transportation from either the Denver or Colorado Springs airports. Your parents don't need to come with you.
The USAFA does not provide transportation from the Denver airport, only from CO Springs. You can take a shuttle bus from Denver to the academy but you will have to arrange it yourself. I flew out with my daughter and rented a car in Denver and drove her to the academy. There were not many flights into CO Springs airport and they were more expensive for us, so we flew into Denver.