Hello there. If you are going to visit with your parents, then a serene getaway is preferred. Go to valley of flowers and Hemakund Sahib for a day or two and then you can spend the remaining couple of days in Mussoorie and Dehradun. Airport and Railways is very easy so it won't be a hassle for you and your family.
If you are planning to travel with your parents than I would suggest you to consider Rajasthan. Since you live in Gurgaon, Himachal and Uttrakhand too are feasible but not in monsoons. Rajasthan looks beautiful in monsoons and is within reach of 5 hours max. from Gurgaon. You can consider Jaipur for your scheduled dates. Thanks!!