First Trip & Honeymoon in India! Help!

Hi, we decided long time ago to spend our 3 week honeymoon in India and with wedding plans coming together, we now have time to plan the honeymoon!

Our original thought was to fly to Delhi, (15th/16th October), to enable us to visit the Taj Mahal and then make our way down to Kerala to explore there, whether that be by train or internal flight. Finally, making our way up the coast, visiting Goa with a return flight home from Mumbai on the 5th/6th November.

Whilst it would be nice to see the Taj Mahal, would this be cramming too much in for 3 weeks and be worthwhile flying straight to Trivandrum and just exploring the south west coast? I'm sure this will not be our first and only visit to India so whilst it would be nice, I could wait a little while longer...or is it do-able??

Once I get the arrival and departure points sorted I can plan the trip further, but stumbling at the first hurdle!! Any advice would be appreciated and any suggestions of where/what to see while we're there also!

Many thanks

3 weeks is a decent amount of time.
I would not miss the Taj ...
Spend a night in Agra (visit the Taj, Agra Fort and Fatehpur Sikri).
Then head back to Delhi and fly down to Kerala. I'd avoid the train ride (it is a long ride, plus not one of the best train routes in India as far as the coaches go).
Cheers!

If you find time, You can also check out Meghalaya (Shillong & Cherrapunjee). For more info check out:
http://megtourism.gov.in/attraction.html
http://megtourism.gov.in/dest-khasi.html
http://megtourism.gov.in/dest-jaintia.html
http://megtourism.gov.in/ecodestination.html

I would suggest 02 nights Delhi- 02 at Jaipur - 01 at Agra- drive back to Delhi and fly to Trivandrum. Explore Kerala for about 7-8 days then fly into Goa for about 4-5 days and lastly at Mumbai for the remaining days before flying back home.