Do you mean 1/4 - 1/8?
I think you're probably fine whenever you go, except Friday evening will likely be significantly busier (but is open until 9 to 11 instead of 10 to 8).
I would think Monday MIGHT be a little busier because some people MIGHT be extending their holiday weekend? Probably no big deal, though.
I believe Friday has the return of a popular fireworks show (Remember...Dreams Come True), so I would expect significantly larger crowds that evening. But you can get lots of Fastpasses early in the day, when
Disneyland is not crowded--the Hub and Main Street very well may be starting to get gridlocked from 7 or 8 PM until the fireworks are over, though.
If you want to see the fireworks and want consecutive days, that means you'd want to go on Thursday and Friday. Friday you can (wind permitting) see fireworks, see the Pixar Play Parade in DCA, and hang out in the park until 11 PM. Despite the potential for crowds, that's probably what I would do.
If you desperately want lower crowds, if fireworks aren't a priority, and/or you do not want to/can't stay past 8 PM, then I would do Wednesday and Thursday because crowds will probably be lower but you could see Aladdin on Thursday. The Pixar Play Parade is offered Wednesday so you could see it then (but not Thursday).
Now, IF you have a child who's really into
LEGO, you might look into this on Tuesday:
LEGO - Mini Model Build
5:00 p.m. to 8:00 p.m.
Visit the Lego Imagination Center and learn how to build a mini model and take it home for free! A new model will be available every month and will be specially themed to that month. Quantities are limited and offer good while supplies last. See store for complete details. (Models are not for sale and cannot be purchased. One free per child. Event is open to children aged 6 to 14 only)
Have a great time, whenever you go!