Judy, going to India in that circumstance, on a cruise, with an escorted tour up to the Taj Mahal is certainly the right way to do it.
I have not been to the Taj Mahal, but everybody who has been there, and in that area of India certainly thinks it is worth it.
I spent a week in Mumbai, and hated most of it; it's a terribly congested city full of poverty and dirt. But the downtown part where you will no doubt be located has its charms. And I still believe that the country as a whole has much to offer--I intend to go back some day.
I believe they have improved the Mumbai airport. If you're flying Business, they have a fairly nice departure lounge--departing from that airport is much easier than arriving.
Stepping outside of our comfort-zone and seeing how some of the rest of the planet live is an enlightening experience. Go for it!