The firing on the fort was done on orders from the Confederate cabinet. Which brings up an interesting question - why didn't Davis go to the Confederate Congress for approval before declaring war on the U.S.? Unlike the U.S. Congress, the Confederate Congress was in session.
Sorry, but the Confederate Congress had been out of session for almost a month when Fort Sumter was fired upon. The first session of the Provisional Confederate Congress lasted from Feb. 4, 1861 to March 16, 1861. The second session took place from April 29 to May 21, 1861.
The first session authorized Confederate commissioners to go to Washington and peacefully negotiate with the new Lincoln Administration over "all matters connected with the public property and the indebtedness of the Government of the United States existing before the withdrawal of any of the States of this Confederacy." Lincoln wouldn't see them. Seward led the commissioners to believe that Fort Sumter would be evacuated, and Lincoln's special agent Lamon told the SC governor the same thing. Once the commissioners realized they had been lied to about Sumter, they accused the Lincoln Administration with "gross perfidy" about Sumter shortly before the Northern battle fleet reached Charleston.
I think you are confused about which president was trying to avoid his Congress. The US Senate was still in session on March 28, 1861. They asked Lincoln whether he had anything of importance to tell them before they adjourned. He replied that he didn't, so they adjourned. However, on that same day Lincoln had a secret order drafted for the battle fleet to go to Charleston. He issued the order to prepare for that expedition on the next day. His cabinet and generals had told him such a mission would result in a shooting war. Was that not important enough to involve Congress?
Davis convened his Congress about two weeks after Sumter was fired on. Lincoln didn't convene his until July 4, well after he had successfully manipulated the country into war.