Now that Epcot is pretty much a year-round festival park, we avoid it on Friday and Saturday late afternoons/evenings. The rest of the parks, well, it depends on what time of year. If MK has a party (Halloween or Christmas) that night, it’s usually not crowded until around 4 PM. I’m not sure about the effects of the paid After Hours parties at MK, DHS or Epcot. Any day that local residents might have off work, such as the actual MLK or Presidents Days, tend to be more crowded, especially MK. But as above, what time of year are you thinking about?