It is not enough only to present the results to decision-makers. Above all, follow-up with the young participants is highly essential. Firstly, you should send the results to them. Secondly, you should keep them updated on the initiatives that are being realised to make their input count, and what impact it has made so far.
In general, your results should be freely available to all interested parties online. However, you should directly communicate the results to all the target groups you identified when you prepared the communication strategy for your project. To get public mention will have a positive effect on your chances for reaching your goals.