If you do consider showing older movies, check the length. Some of the classic family movies are a whole lot longer than our kids may be accustomed to. Sound of Music, for example, is nearly 3 hours long!
If I understand most of you correctly, you get bettter results showing newly released movies, right? I was thinking about showing something older because I figured I'd have a better turn-out with something they haven't seen, but it seems the opposite is true. You've given me something to think about.
In our experience, the best movies to show are ones that have just been released. We always do our movie nights the Friday after a popular kids movie was released (the Tuesday before). Like "Robots" would be good to show now since it just came out last week - it's new for the kids and they haven't seen it a million times. We are having ours on November 11th. Charlie and the Chocolate Factory will be released on November 8th. Madagascar will be released on November 15th - so the 18th would be a great day to show that one. We sell refreshments - we make on average $1000 per movie night. Once we showed an "older" movie and had a very small turn out - we made around $250 that night. Our school has a license for the year (first year we got that) - but in the past we've always purchased a one time license for $50. It's good to be legal.
You can do a Yahoo search to find out what movies are released when... type in "november 2005 dvd release" - there are several sites that have that information. Or check out blockbuster's site for "upcoming releases".