Delhi-Chandigarh-Manikaran-Manali-Agra-Delhi

Hi friends,
Myself and a bunch of my friends (4 in total) r planning for a 8 day tour of North India (manali in particular) during the 1st week of October.

Here is our tentative itinerary :
1) 29 Sep : Morning Reach Delhi by Flight
Visit some tourist spot if possible. Catch Shatabdi Express to Chandigarh in the evening.
2) 30 Sep : Chandigarh Sight Seeing.
Evening board a bus to Manikaran
3) 1 Oct : Morning Reach Manikaran. Take some rest.
Sight Seeing. Stay there at night.
4) 2 Oct : Go to Manali and Check in some hotel.
Manali Sight Seeing.
5) 3 Oct : Rohtang Pass and Manali Sight Seeing.
6) 4 Oct : Still in Manali
Evening leave for Delhi
7) 5 Oct : Morning Reach Delhi. Check in. Visit some places in Delhi.
8) 6 Oct : Morning Hire a cab and goto Agra. Taj Mahal. Reach Delhi by Night. Glimpse of night life in Delhi.
9) 7 Oct : Afternoon. Catch flight back home.

Is this itinerary feasible? We r budget travellers and do not want to spend more. So please suggest some cheap but decent lodges/hotels in manikaran, manali and delhi.
We have got less than 2 days in delhi. what all places can we visit there?
Manikaran + Manali We have got about 4 days. is it enough? What other places r there nearby manali which we can manage to visit?
Also is the Chandigarh to Manikaran bus journey too tiresome? do we get sleeper seats in those buses/volves? do we need to book in advance now itself?
Any suggestions/comments/replies would be really helpful.

Rohtang pass is avoidable--very windy and cold and little to see. Much better is to enjoy pony ride in Solang.

the drive to Rohtang from manali is very scenic and if you would like to avoid the crowds drive till gramphoo and you'd get to see some amazing vistas.

hey thanks so much vmehra and rishabh.
i also want to know whether 3 and half days r enough for manali and manikaran including visit to rohtang pass (if we take it)? and if time permits what other nearby places r there to visit other than Solang and gramphoo and also how far r they from manali.
Also pls suggest some bugdet but decent hotels for accomo in delhi and manikaran. we have already made bookings for manali.

Well 3 weeks are not sufficient for Manali and surrounds. There are many short hikes up the Solang Nullah.
Manikaran is also good. Could have short hikes along Parbati. then temples ok kullu etc