Every hillstation is going to be extremely crowded, why don't you try going to places like Udaipur, Jaipur, Jim Corbett or Gushaini? I'm sure you'll have a great time!
Depends on your budget. One can reach Rishikesh, Dehradun etc. from Delhi. Even shorter getaway could simply be some resorts in Manesar or Neemrana fort. I am utilising this weekend on a trek in Himachal.