Friends of ours went to Vietnam at Easter two years ago - spent some time in Ho Chi Minh City, then to Hanoi, then to a beach resort at Hoi An.
All the domestic travel was by air - I think Vietnam Airways, although it can be done by car/taxi if you don't mind long trips over often-rough roads.

She said HCM was the 'cultural' part of the trip, Hanoi the shopping bit and Hoi An 'the holiday'.
Not sure of the HCM or Hanoi hotels, but she stayed at Victoria Beach Resort at Hoi An and said it was fab.

We're considering the idea of going next Easter.