I think road travel is not a good idea. There are trains available to Dwarka and Somnath from Ahmedabad. Somnath and Dwarka both are connected by the train as well. 

The train name and number are SMJH OKHA EXPRESS (19251).

But if you want to travel by road then you can hire a local travel and tour operator, you can find these operators on Justdial.

Suggested Itinerary for your trip is listed below-:

Day 01-: Ahmedabad to Dwarka (8-9 hours)

Day 02-: Visit Byet Dwarka and Nageswara

Day 03-: Visit Harshad Mata temple and Porbandar then head back to Ahmedabad.