GOod Question - we will be there Saturday - Tuesday and we are expecting the lease crowded day to be Tuesday. I would think maybe Monday would be the least crowded especially towards the end of the day with people heading back home - but this is totally just me guessing.
We'll be spending full days at the parks Fri, Sat & Sun. I was expecting Friday to be medium, Sat to be extremely crowded and Sunday to be crowded. But, since this is my first trip to Disneyland, I am basing it on years of Memorial Day experience at WDW. So, I might be wrong.
For what it's worth, Memorial Day Monday is usually very uncrowded at WDW's Magic Kingdom for some reason. The last two years we "walked-in" with no PS to lunch at peak time at Crystal Palace.
We're planning Thurs - Sun that weekend, however I know a few families planning Mon - Tues, with the same thinking about the weekend being more busy than hopefully Monday. I would expect crowds either way at this point.