Get a project planned to keep interest high. Instead of using kitbot frame like last year, you guys could plan a different drive system or expanding your four wheel drive into a six wheel drive.
Take what you learned last year, and pick out the good things, and then try and teach it to them.
For programming, (FIRST SAVE THE CODE SOMEWHERE), you can clear out your controller from last year's bot and have students use EasyC to reprogram it.
Assuming you have different committees, (Electrical, Mechanical, Programming), have the leaders of these committees each come up with something fun to do which teaches these new guys about robotics.
Something that doesn't hurt, if Miss Daisy (Team 341) is still doing it, contact them and see if you can get a copy of Team In a Box.
http://www.team341.com/tiab.html
If you're really up to it, try disassembling last year's bot and help the newbies reassemble it.
As far as what to say though, I would try and show them clips of last year's matches. Whether you were in them or not. You could check The Blue Alliance (thebluealliance.net) and stream some clips if you have a projector.
It's really up to you guys though. I would create some sort of entry form and hand them out at the meeting. Stick some flyers up around the school. Make sure you emphasize the fact that no mechanical or computer skills are required.