Facilitating an effective ideation session is as much art as it is science. Now is the time to go wide and dream up anything and everything that might help. Some tips for facilitating this are below.
Consider: How might you best create a creative environment for ideation?

Invite multiple perspectives. Bring in people from different backgrounds. Include your audience as co-designers. The more diverse your group, the more creative the ideas!
Review the problem statement and program outcomes. Ask if there are any questions or clarifications. Ask the group, “How might we address this?”
Ideate away! If you are in person, list topics on posters and giving everyone sticky notes to write as many solutions as they can. Virtually, use an online ideation tool, or introduce a topic on the screen and have them add solutions to the chat. Keep it lively and upbeat by highlighting great ideas as they come in.
Go for quantity over quality. There will be time to refine ideas later, for now, your goal is to generate as many ideas as possible. Now is not the time to have a feasibility conversation for any one idea. Gently prompt the team to move forward and generate more ideas.
Surface ideas with the most potential. Once you have exhausted your team’s creativity, have them review each other’s ideas. Give them each 10(ish) votes and have them vote on the solutions they think have the most potential. Explain that their ideas will significantly inform and inspire the prototype.
“If at first the idea is not absurd, then there is no hope for it.” — Albert Einstein