If you are not beach fans, I would still visit Goa for a day, then head to Agra. Jaipur and Udaipur are nice towns, but the Taj Mahal is absolutely incredible and is not to be missed, especially this year due to its anniversary and celebrations surrounding that.

Traveling by car from Delhi to Agra takes around 3-4 hours, depending on traffic. The roads are good, though. Train might be faster, depending on your tolerances for the train stations in India.

But from Goa, Udaipur is much closer and also has nice attractions, including the Lake Palace hotel (seen in James Bond's Octopussy movie).

Bottom line, in my opinion, is not to miss the Taj. If you can, stay at Amarvilas hotel, inside the "clean zone". It's expensive, but completely worth it, if not just for the view. The service is amazing as well.