Well I finally took the plunge. Last night I had the first showing of the outdoor "Cinema and Drafthouse". Although it was probably extremely meager in comparison to most on these boards, it was a great time and well worth the effort!
Here are a few after thoughts for those still considering:
Projector - Used Panny 900 from my indoor set up and it worked well. Fairly simple to disconnect from indoor mount (four screws) and more than bright enough for an evening showing.
Screen - Gemmy 149" Inflatable (courtesy of JoeRod) - Extremely easy set up! Literally took less than 15 minutes. I can see the need to possibly go bigger in the future, but the simplicity of this screen will encourage frequent showings
DVD Player - I used my PS3 and it worked extremely well.
Stand - Actually used our trash can for lack of a better last minute option. Yes it was kind of tacky, but the height was good and it was easy. Need to find something better next time.
Speakers - Originally I thought I would start with only a front left and right, but after testing I determined that a center speaker was also essential. Next time i think i may try surrounds and a sub (happen to have an old svs sitting around), but certainly agree with others that just about anything outside sounds pretty good. I was using extremely old Sonys and it sounded great.
Receiver - Out of necessity, I used my Denon from my indoor setup, but would like to eventually purchase a cheaper dedicated receiver just so I can minimize disconnecting and reconnecting set up time.
Wires - This was definitely the biggest headache. I've already ordered banana plugs to cut down on set up time and with eight adults (drinking margaritas) and seven children, I was constantly worried about someone tripping over them. Until I can determine (and afford) a permanent site and bury them, I'm trying to come up with an idea for some kind of large sheet/blanket to lay over the viewing area.
Viewing Material - The PS3 was great for showing current (downloaded) movie trailers. I also put together an intro using professional voice overs (purchased from this forum) along with various pics and graphics which was a huge hit! Didn't have time to put together a slide preshow, but may try next time. I know a lot of people are worried about the flow without having multiple dvd players or a htpc, but i found it pretty easy to simply eject one dvd and insert the next.
Overall it was a great time and the goal is one showing a month until it gets too cold. Thanks for all the advice and and suggestions or comments are appreciated!