I would suggest you to shimla because it is well connect by car (6-7 hours from car )and direct train from delhi.and cheap stay and many hill spot near shimla.
- The Green World
- Visit to the Kufri Fun World
- Horse Riding at Naldehra
- Visiting the statue of Lord Hanuman .
You should go to Dehradun - Landour - Mussoorie for a 2 day trip. Landour is a lesser travelled place and there's a small trek from mussoorie to landour.
Try Ramnagar - Corbett national park.
Since it's a two-day trip you can go on a road trip to Agra, Chandigarh, Jaipur and even Mussoorie!