At what restaurants will my family of four have the best chance as a walk up? I've got ressies at Kona, so we are going to try to see if they have any cancellations at 'Ohana, even though I know it is a longshot.
I have no idea about walk-ups, but another idea would be in the AM before you head out, call reservations and see whats open that day for the park you are headed to. We did this last trip during free dining with great sucess.
Don't know if you'll be able to see this in WDW (since you just left), but check-out Biergarten! We love that place & they are almost always accepting walk-ups.