My reply is a bit late for this year but for future consideration. . . . . . . .
I wouldn't try to use youtube video. It is just too low quality to try to show on a really large outdoor screen.
Each year I create different scene compilations for the trick-or-treat crowd.
I create a mix of Halloween theme movie cartoons - Disney's "Trick or Treat with Donald Duck is an example and also Casper cartoons and scary movie scenes.
Each year's dvd is around 20 minutes long and I set it for auto repeat so once I have it playing I don't have to mess with it until I turn it off. I use an old but good stereo PA amp and a couple of small PA speaker "towers" and it's pretty effective and always gets a lot of positive comments from the kids and their parents.
The editing/dvd creation is pretty simple and the regular definition dvd scenes look clear and good on a 15X15ft. screen.
IMO - a LOT of content uploaded to YT was put there by people who don't own it and without the permission of the owners. I haven't read about law suits or arrests for those zillions of folk and I doubt the MPAA is going to pursue anyone putting a few cartoon or horror film clips on a wall screen on Halloween night - wouldn't cause me to lose any sleep.
I will try downloading a few YT clips and check out how well they stretch across the 15ft outside screen - could be I'm mistaken about the quality of the newer stuff that's out there. The standard def MPEG2 dvd clips I've been using look really good - in my situation, many of the kids and their parents stand a watch several minutes - the sound is good - it's always a hit each year in our neighborhood and if the Y.Tube stuff works good that would be great - it's a lot easier to pull from Y.T. than what I've been doing and a lot more variety of content to choose from.
I went to Wally World and bought the cheapest FROSTED shower curtain they had (think it $2.99). Cut off the bottom with the magnets, then got some black plastic (the stuff that comes in the rolls) and created a border around the curtain big enough to attach to the walls just inside the garage. I just duct tape mine together. You can't see the tape through the plastic and it only has to last a couple of days at a time I've used mine for 3 three years now and just re-tape where and when necessary. If you attach the screen BEHIND your garage door rails, you can set it up and close the door until ready to show.
I had people stop by and ask where I got a plasma that big.
Let me know if you want to drop by to check mine out. Once I get it set up that is.
Last year I tried the Haunted Mansion singing pumpkins thing (the Grim Grinning Ghosts song) but I couldn't ever get the singing to sync up with the video. I would get it to look really good and then when I burned it to DVD it would be out of sync.
I forget where I got the video. That could be it. It cost about $20. It wasn't a problem with the video, it was a problem syncing up the soundtrack. I could sync it up and it would run great on the computer, and then when I burned it, it wasn't in sync. Seems to be working now.
Did you find one that has the audio already in it? Everyone I've come across only has the video. Appears as though everyone is afraid of repercussions from Disney if they sell both together.
I got my Singing Pumpkins to work! Set them up Sunday night and it looks great. I'm not leaving the projector and player setup out all the time and it rained just enough Monday night to NOT put it out.
I found a hay bale for $7.00, used the three fake pumpkins and "toy" projector I bought last year and my $29 outdoor-use-only DVD player. The "projector" (and I use that term loosley) has built in speakers, which work surprisingly well for this purpose.