We have used these and they can get pretty crowded on their own. I would still recommend arriving early so you can stake out a spot at the front and sit on the ground so you have open space in front of you. They usually just keep packing in the wheelchairs until the roped off section is bursting. It will be just like staking out a spot on a curb somewhere as far as crowds behind you, in fact the CM might even try to put the wheelchairs in front of you if you don't have one (they did this to us once at WDW. I ended up standing the whole parade. Not fun!) Have a great trip!