I've done the CHOC walk and stayed at the park the past few years, but only because I'm a Premium AP. While that day does have a higher attendance than a normal weekend in that time period, it isn't a huge increase. And the slight increase would only be Sunday.
If you have any interest at all, you should participate! There are a lot of people cheering on the sidelines and characters are all out along the course for photo ops, and you get to go backstage in some areas few people ever get to go. It is a lot of fun!!!