Back in 2004, I did Disneyland and Knotts Berry Farm over labor day weekend. On the Saturday before labor day, I went to Disneyland from 4pm to midnight. I just got into the LA area an hour beforehand (thats why the late start). The park wasn't very crowded at all. Not a long wait for anything. Fantasy Land was empty after 9pm, so I did all the kiddie rides.
On the Sunday before labor day, I did KBF. In the morning it wasn't too bad, but it started to get crowded in the afternoon. Left at 6pm.
On labor day, I did Disneyland/California Adventure (started off at DL, then CA, then back to DL) It also wasn't crowded at all.