RMM, you didn't give your dates, so hopefully my info for SMneer and ozsammyboy will help!!
Hello ozsammy...I mostly know LL, my DD is 7, so haven't done MM yet. I absolutley HATE Knotts Berry Farm..so can't speak to that topic either. But, LL, I know. Weekend days will obviously be the busiest during your time frame, but as compared to other parks, probably not as horrible. Weekedays are not as busy. I went last year on the 27th, and we rode everything we wanted and did not get too irritated with lines. Since we go all the time, a 15 minute wait is enough to wrinkle my day!!! The lines for the rollar coaster will likely be 30 minutes part of the day...but there are really a lot of things to do, that are not rides. There is a big redwood play structure which will take up 40-60 minutes, many places to just play with Legos, shows, an imagination zone....so can keep pretty happy.
Depending on the age of all kids...will dictate things as well.
Anymore questions, I will be happy to try to answer. I am not an authority, but go about once a month!!! Oh, and am inpatient and hate crowds..so that likely colors my opinions!!!
I hope you all have a great time at LegoLand!!! Amy