Presidents weekend will be extremely crowded at WDW. We are going to be there at the same time...I am hoping that the rest of the week will not be too bad. Make plans to use EMH if you are staying on property, and definitely use fast pass. As far as the 26th, that is a Saturday, and weekends often bring local crowds to the MK. That weekend is also ESPN weekend over at MGM, and will be going on Fri.-Sun.
Have Fun!