The dates for the "big" marathon weekend is Jan 7-9 (5K Friday, half on Sat, full on Sun). The Princess half marathon is March 6 (with a 5k on Sat March 5).
I did the Goofy this year and went by myself and did spend time in the parks before and after the races. There were quite a few people wearing medals in the parks and talking about the races so I'm pretty sure that most people running (and their families) go to the parks.
The crowds were pretty substantial for a January weekend (especially with the ridiculous weather we had this year!)
Jill