My organization sets up for slide/video presentations in a lot of different spaces. I've found that having a short-throw projector plus a dedicated projector stand makes it easy to get it set up in a variety of configurations.
Standard projectors require you to place the projector 6–10 feet from the screen, which means you need to create a gap in the seating to accommodate. And the cables (power and video) need to be run even further, and generally across an area where people walk.
Short-throw projectors work just 2–3 feet from the screen, so you can put it in front of the seating. And it is a small enough gap that no one will try to walk between. You can also get an ultra-short-throw projector if you want to put it even closer (<2 feet). I bought an Optoma, and I'd recommend that brand.
I also recommend a Pelican case to protect your substantial investment.
For the screen, if you are looking for portability and value, blackout cloth is the way to go. I do have a proper 16:9 screen, but it is very long and won't fit in most cars. The cloth can be rolled the short way and works great (as long as you have a variety of clips, cord, and braces to mount it).