Rest of the week should be one of the lighter weeks of the year as all the holiday festivities will have concluded and everyone is back at school/work from the vacations. 2nd week of January thru end of February is about as good as it gets at Disneyland. Parks are pretty much busy from spring break all the way thru New Year's these days. Even the next two months are busier than they used to be, but the best you'll get.
Edit: I should add, though it's rather obvious -- holidays/holiday weekends during this time will still be packed.