Do Not Breach
You have decided not to breach the blockade. The ships carrying the second supply of missiles are holding just outside the blockade, waiting for your next move. The entire world waits for your next move.
After sitting down with your advisers, you determine that there are three possible options facing the Soviet Union now.
You hold the fate of humanity in your hands.
You could secretly try to reach a deal with President Kennedy. Perhaps, if you agree to remove the missiles from Cuba, he will match that by agreeing to remove the missiles from Turkey. This would seem as a win-win on the surface, however it would likely be political suicide. It would appear to those back in the U.S.S.R. that you gave in to Kennedy. This would likely have bad repercussions.
The missiles on Cuba are ready to launch. They were put there for a reason and there is no better reason than to strike the U.S. before they strike you. Kennedy has been playing a dangerous game. Kennedy wants war. First it's a blockade, next it'll be troop movements, after that... who knows? The Soviet Union must react before we are caught off guard.
More information must be gathered before a decision can be made. By flying a Russian spy plane over the U.S., similar to their U-2 missions over Cuba, valuable information regarding their intentions may be able to be gained. If the plane is discovered, it will certainly strain tensions even more, but it could also work out better by forcing the United States to make a move first. That would allow the U.S.S.R. to look as the victim in the eyes of the world.