Lauren,
My favorite Wordle alternative is
WordItOut. I like it because it works on our chromebooks (and Wordle doesn't).
I have also played with
Taxedo and
Tagul. All three of these sites let you generate clouds from websites--SO, while the cloud generator won't let more than one person type on it, perhaps you could make have a google form or doc in which people submit ideas and then copy and paste the information and then input it? Even fancier, you could "publish" the google docs as webpages and put that URL into the cloud creator.
Good luck! I'm sure it'll be fabulous :)
-Janet