I want to go to mussoorie for a family trip in the coming month of
April or May. we will be 6 adults and two children. We will start from
Delhi and would like to go by parsonal taxi. We intend to stay for 2
to 3 nights in mussoorie and also would like to cover haridwar,
rishikesh, on the way, may be we can spend one night in Dehradun,
haridwar or rishikesh if it is worth spending. If anyone can guide me
about the exact route taken, how to cover all, and above all where to
stay especially in mussoorie, so that either all of us stay in one hut
type of accomodation in a good resort or family type accomodation in a
good hotel; which should be comfortable uto a level of 3 or 4 star
accomodation.

If any other specific information from my side is required, please let me know.

Answering a question like this is impossible without investing much
time and work. You might want to have a look at the Google Answers
pricing guide:
http://answers.google.com/answers/pricing.html

This looks like a really good place to start:
http://himalaya-holidays.com/p-t-8.htm

you can cover haridwar/rishikesh in one day  and see laxman jhula