Check the book Operation Anadyr, which tells the story of the Cuban Missile Crisis from the POVs of an American officer at the Pentagon and a Soviet officer on the General Staff who was en route to Cuba by air when the missiles were first discovered. The book reprints a message sent by the Soviet Defense Minister, Marshal Rodion Malinovsky, on 22 Oct 1962, which stated that the Soviet Forces in Cuba were to be prepared to fight, but "without Statsenko's means and all of Belodgranov's cargoes." General Igor Statsenko was Commander of the Strategic Missile Force in Cuba (the SS-4 MRBMs and the planned SS-5 IRBMs that were en route), while Col. Nikolai Belodgranov was in charge of the storage depot where all the tactical weapons (FROG missile warheads, FKR cruise missile warheads, and gravity bombs for Il-28 bombers) were kept. What this meant is that the existing protocols for launch of the MRBMs-only on Khruschev's orders-were still in force, and that the previous authority to Gen. Issa Pliyev, CINC-Soviet Forces Cuba, to use the tactical weapons at his discretion, had been revoked. This message was repeated on 27 Oct, where it was categorically stated that the FROGs, or Lunas as the Soviets called them, the FKRs and the air-delivered bombs could not be utilized without permission from Moscow, and that Soviet Forces Cuba was to confirm receiving this order, which they did. The Soviets actually were preparing to disable the tac nukes when the crisis did end. The Soviet officer who prepared this part of the story was then-Col. Anatoly Gribikov, who retired as a full General.
So unless the Cubans manage to grab a warhead or two, and launch it, the war in Cuba stays conventional. However, the Soviet subs had nuclear torpedoes (10-15 KT yield) and the ROE were quite vague as to using the torpedoes. The Soviet Navy was frantically trying to contact the subs and tell them that nuclear release was now firmly in Moscow's hands, but not all of the boats got the order until 30 Oct. Give me a couple of days and I'll post the U.S. invasion force's OB for XVIII Airborne Corps and II Marine Amphibious Force. 100,000 Army troops and 40,000 Marines, backed up by 850 USAF, Navy, and Marine aircraft in Florida, and over 100 ships, including four attack and three ASW carriers. The Soviets themselves admitted later that if the war stays conventional, then Cuba is overrun in a week to 10 days. The U.S. plan called for organized resistance to end by D+18, with U.S. casualties expected to run about a thousand a day for the first 15 days. 1,190 air strike sorties expected to fly on A-Day, with D-Day in Cuba expected eight days later.