Right after kickoff, I wouldn't even worry whether an idea was against the rules or not. Just get all the ideas out there. If something sounds good, you can research later to see if it is legal.
Everyone on the team should be able to make suggestions. If you have a small team, you can do it all in one group. Or you might break up into several groups, so everyone gets a chance to give some ideas.
Write everything down, probably on a whiteboard or flipchart. Rules: ideas only, no evaluating or arguing. Other people can ask questions only to clarify the suggestion.
And JVN's blog gives a great perspective on deciding WHAT to do before you try to figure out HOW to do it:
http://blog.iamjvn.com/2011/01/jvn-b...efore-how.html