I'd say it's certainly much longer than 10 minutes myself. But honestly, I don't feel like it's that bad. Seriously, folks will walk way farther back and forth inside the ICC than that distance.
As as far as sidewalk quality: Presuming no construction starts up between now and the con, it should be just fine. I'd honestly say that crowding will be a bigger issue for a mobility scooter than the sidewalks itself.