The best resource available for this unit is the New York Times website. It has an extensive archive collection that can be accessed by day, month or theme so that you can decide how your class will approach early April 1861. Students with independence and ability can take on the day–by–day searches of the Times while other students may need more guidance.
The Library of Congress also has a website, http://chroniclingamerica.loc.gov/, which includes newspapers from all over the country. These can be used to supplement the Times, especially with a view to providing regional perspectives on the events of April, 1861
One area I am concerned with is how to tie April 1861 to the rest of the Civil War. Film can be great in doing this given the limited time available. Some great ones are
Glory, Gods and Generals
. Ken Burns' famous documentary
The Civil War
would be too long in its entirety but parts of it would help connect students and the work they've done to the rest of the conflict.