That week (beginning the Friday before Presidents' Day and continuing to the Friday after) is very crowded, comparable to if not worse than a mid-summer week although quite a bit less than Christmas, the two Easter weeks or the week July 4 falls in. In other words, do not assume Presidents' Day itself is the one to worry about because that day isn't any better or worse than the other days. That week has simply become a key vacation week for WDW (and not just a weekend). You usually get some extended hours which alleviates the crowd somewhat but during peak times of day (10 to 4) you are going to see lines at popular attractions of 75 minutes and longer and it does not drop much into the evening.
You really need to consider strategies and not just head out to wherever you might desire on any given day at any given time. For example: (a) going early, including when a park opens early to resort guests if you are a resort guest, is advisble because during the early morning you can get on a lot without large crowds; (b) going very late when a park is open three extra hours to resort guests although those are usually crowded until about the last extra hour; (c) if the park has that extra hour in the morning, go to some other park in the late morning to afternoon because the early morning park has a lot showing up simply because it opens an hour earlier than normal and then the "normal" crowd comes later to compound the issue; (d) sometimes between 4 and 8 at MK you can get on things, like Pirates, Haunted Mansion, Jungle Cruise, or other secondary attractions with small lines though they have long lines from 10 to 3; (e) likewise at Epcot, almost everything becomes a walk-on after 3 or 4 except Test track, Mission Space, and California Soarin -- in other words that 50 minute line you see at Spaceship Earth at 10 is non-existent at 3; (d) at MGM after 4 you can get relief at a lot of the attractions other than Mermaid, Tower of Terror or Rock n Rollercoaster; (e) if they have two Fantasmics at night, either get the dinner package for the first one or go to the second one -- the first one is always packed to the gills and people are rejected, the second one never fills; (f) make dinner (evening meal) reservations for any park restaurants well in advance and for resort restaurants make them by about a week in advance although those can often be had by day before ressies; (g) use fastpass as much as possible; (h) consider some other activities rather than just the parks like Hoop Dee Doo, Cirque Du Soleil, the Polynesian Luau for which you will get in if you make the ressie and will feel relieved from a hectic park day besides seeing a good show.
As to KSC, I would not think it would be hugely crowded since that usually occurs only during launch times.
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