Since you have asked only two places in Himachal to visit, I would suggest Kasol, Spiti valley, Mcleodganj, Dalhousie and tirthan valley. There are some places you can cover inbetween like Fagu, jibhi, tosh, chail, Kinnaur and Nahan. Manali is no doubt one lovely spot, while Dharamshala is must to visit. From Shimla nearby spots are chail, Narkanda, Nahan, naldhera, kiarighat, and karsog. From Manali nearby spots to visit are Kheerganga, Sethan, marhi, gulaba and Malana.