Also, is it likely to be hot then(April 6-13), as in over 85 degrees?
Nope, April is very much a Goldilocks month. We arrive April 12th for the start of a six month trip to Canada's Maritimes.
As far as scenic DE goes, the old part of Dover is like stepping back in time, as is going through the old section of many of the smaller towns. The history of the area goes back to the 1600s. Rehoboth is a seaside town with a boardwalk, hotels, motels & it's share of touristy stuff. A long long day if planning a round trip from DC. Much better to make a few days of it & pick a CG.