Instead try Club Mahindra in kanatal. Ditch Mussoorie let it rejuvenate and head to Chamba, Tehri, Kanatal each for 1 day and 3 days in rishikesh. If you could go higher, then in october end Nag Tibba and Deaorital tal would be best. If interested, you can reply me and i can come up with a detailed plan. PS i belong to rishikesh.