If you will be driving to the Cape Canaveral area on a Wednesday or Thursday morning, you usually can pre-book a free tour of the Cape Canaveral Air Force Station that takes you to most of the sites associated with the US manned space programs from Mercury, and through Gemini and into the early Apollo program. This TA thread explains the details: tripadvisor.com/ShowTopic-g34117-i877-k47812… . This tour does not involve a visit to the KSC visitors' complex and should be booked in advance. The tour is sometimes not available around holidays, or when the CCAFS is awaiting a launch, like it was yesterday (January 19).
The tours offered at KSC require admission to the visitors' complex there. A standard tour of the KSC is included with admission, but it does not include any of the early manned programs' launch sites. Two optional, extra cost tours are also available -- the "Then and Now" tour is very similar to the free one at CCAFS mentioned above. The "Close Up" tour is the one that currently includes a visit inside the VAB, an experience that had not been available to the general public in over 30 years because of the shuttle program's requirements.
More detail about the KSC visitors' complex experience can be found at tripadvisor.com/…37718590 . It is possible to do both the standard tour and a single optional tour in the same day, but you must arrive early because the availability of the optional tours is limited. KSC opens at 9 a.m. and I would allow 60 minutes driving time from the Orlando airport area and more from the Disney area.