DH let them watch episode iii last weekend while I was at work, I wasn't happy. 3 year old loved Darth Vader getting put together and wasn't phased by the horrific burns and slaughter of children. DS6 understood about more but was OK watching it. They've watched all the other Star Wars movies.
Older DS went to Star Wars b'day party the night before where the b'day boy (7) saw Episode I for the first time - no way DH could have held out that long.
LOTR I might let him watch in a few years, I was horrified my sister let my nephews watch them so young but fmy view has changed, DS is able to make the distinction between movies and reality , when I was a kid I'd get nightmares after watching movies