Kheerganga is good for treak..and if you want a small trip to Himachal for 3days, then you can choose Kasol and Tosh.. it will be a good travel option for 3days
For 3 days there are following options for a Himalayan trek in Himachal Pradesh.
Chandrakhani Pass
Hampta Pass
Beas Kund
Bhrigu lake
Always go with a local guide. Travel responsibly!
You should go for Chandrakhani pass Trek,as november to feb is one of the best time to visit here or you can either visit kareri lake trek,it can be easily covered in 3 days and nov. is the time to go here
Try Kareri lake trek, affordable- good connectivity-and still a cleaner trek amongst the ones which are easily reachable (hope it's still clean and remains the same)
happy Travelling