Working very closely with your champions to make sure an event like this comes off well is really important, and it takes time. Be prepared to do 90% of the work yourself, to be the one with the action plan and agenda and be responsible for making sure tasks are assigned and completed. As this is in service to your cause and campaign, with support and leadership of your key allies, think about the proper care and feeding of your leaders and the folks who are with you. You cannot take them for granted! Giving them the opportunity to show up, look good, do good, while you have done most of the work behind the scenes is okay. In fact, it is better than okay, it is a success!
Even if no reporters show up (which is very common), you can create a buzz after the fact with photos, social media posts thanking and tagging sponsors, and even letters to the editor (with photos) to the local press. Making noise and making sure your champions and allies look good yields positive feelings and draws the attention of key decision makers to your champions. You make champions look good and you become noted as an organization that is good to work with. Key decision-makers understand that good will multiplies, that hero opportunities exist for them, and that the groups involved are wonderful friends to have.