Crowdsourcing, defined by the Oxford Dictionary as the process of obtaining information or input into a particular task or project by enlisting the services of a number of people, either paid or unpaid, continues to gain momentum, both within the event world and out. Take for example, the concept's expansion into other sectors with entirely different goals, such as crowdfunding sites KickStarter, Crowdfunder and Crowdrise, which raise money for products, companies and charities; or this fascinating article on the CIA's Good Judgment Project.
Strongly consider collecting initial ideas from the group anonymously. In internal meetings where everyone pretty much knows one another, people can still be shy about submitting their honest ideas, even if they are able to do so electronically rather than verbally. Once you decide to crowdsource any portion of your event, make it easy for your attendees to suggest ideas by utilizing technology, implementing a smart process, and doing plenty of promotion.