Not with Lincoln running the ship. By April 6th it was too late to stop it. Pensacola was the intended place to start the war militarily. Charleston was a political bonus; Lincoln was taking a big gamble that his actions would provoke it there. If the war started at Pensacola, as planned, the actions the Federals would have had to take would clearly put the blame of starting the war on them.
But these actions may not have started a war if Lincoln did not call for states to invade other states afterward.
There was a period the war could have been adverted as late as March if Lincoln did not send in those ships.