You can explore manali in just single day.. if your friends are with you rent A car or bike and visit the Prashar lake in kullu... it will be awesome experience.... there is only few buses to there thats why i suggest rentals..
You can cover these following places
1. Vashist Temple
2. Old Manali cafés
3. Trek to Jogini Waterfall
4. Hidimba Temple
5. Mall Road
6. Solang Valley
7.Rohtang Pass
Stay on a high range Homestay behind Hirimba Devi temple where nobody can disturb you and feel the nature. Offbeat places always have so many things to get explored by you and you will have so many stories after all to share with your friends and families after the trip !!