You can go to Mussoorie. it's a great place for weekend trip. weather is awesome. To travel from Delhi to Mussoorie by road, take the route via Upper Ganga Canal Road. The distance can be covered in about 6 hours. The nearest airport to Mussoorie is Dehradun’s Jolly Grant Airport. Or 2nd option is Kasol. it's also a great place for its breathtaking views.
Deepends on which weekend you are planning. in case this is any weekend with continuous Holidays , all the destination nearby will be highly packed. But considering you don't want to be part of huge crowd, travel a bit farther and check Mukteshwar..You won't regret the view of Himalayas from the place..