I'm fairly new to DMing 3.5, but I'll say these things.
1) Read this: http://www.giantitp.com/forums/showthread.php?t=150252 It's the thread I started when I was having trouble. Olescamo's guide to DMing (linked on that page) is also good

2) Mooks are fine except that they're kinda vulnerable to one-hit wonders (a big problem with a group this size is the number of attacks) A small number of good enemies might work well?