I hate crowds, and try to go during the least crowded times of the year. However, I have been at super crowded times in December, as well as the middle of summer. I will never do summer again. I have learned that I can handle heat, and I can handle crowds, but I cannot handle both at the same time. It was too much and I kind of do regret going. It left kind of a sour taste in my mouth.
That's why I am going back one last time before my AP expires, the week of Thanksgiving. I know that it will be crowded, but I've dealt with that before and it's not a huge deal to me as long as I don't feel like I am going to pass out from insane humidity.
I have found that the crowds only really start to become a serious bother around parade times on Main Street, or around Fantasmic! show time in New Orleans Square. I also try to avoid entering/exiting Tomorrowland on the Main Street side in the afternoons, as there is a huge bottleneck right in front of Star Tours and Buzz Lightyear that crams everyone together into a small space. I've had more than one leg bruise due to strollers/wheelchairs in this area. Typically I do Tomorrowland first thing in the morning so that I can ride Space Mountain and Star Tours repeatedly with minimal lines, and so that I can avoid Tomorrowland later in the day.
Otherwise, even on really crowded days people are dispersed enough that it's not a continual nuisance. As already mentioned, eat meals during off times. This not only means shorter lines for food, but also means that you will have shorter lines/less crowds elsewhere while most others are eating.
Take advantage of FP and keep checking wait times through the app of your choice. Head to whatever has the shortest lines. On really busy days, certain rides tend to break down more frequently (Indiana Jones, I'm looking at you). If you are paying attention, you may be lucky enough to get in line just after the ride has re-opened.
Another good strategy is starting at DLR when there are no crowds, then moving over to DCA in the afternoons. The paths are built wider there, so even high crowds feel like much less people than at DLR.
You will find other strategies along the way just based on observation. For example, you will probably notice that the wait for the train is always longer at New Orleans Square and Toontown, but practically non-existent at Tomorrowland station. And certain paths are less crowded than others; when moving from Fantasyland to Frontierland/New Orleans Square, go the back way past the Big Thunder Ranch area, or go through the Fantasy Faire area, don't go through the more crowded Main Street.
If I were you, I would not cancel just because of crowds. Especially with 5 days, I think you will have plenty of time to explore what you want to. With just some slight schedule adjustments, you will be ahead of the pack and can really enjoy your trip. And hey, if you get really sick of navigating the parade crowds, just plop down and join them! Have your designated runner go grab some corn dogs (or my personal favorite, chimichangas) and relax for a bit.
. We are planning our second DLR trip for the second week of June and I am expecting some heavy crowds while we are there. Luckily we will be staying onsite (VGC) so we will be able to utilize the EMH. We are also planning on taking lots of breaks in the afternoon when the crowds are at their highest, and I have already told my DH that he has to make sure he has his running shoes on because he will be running for FPs...he loves the fact that DLR still does paper FPs because he knows how to really utilize them.
