Plan a night just for the elders of your church (You can even send invitations made by the youth to the elders). You can have the youth serve them a nice meal dressed in nice clothing (banquet attire). You have the youth share with the elders about how they appreciate them. They can read poems, perform a song for them and read scriptures showing the worth and importance of the role of an elder. The youth can hand out letters of appreciation to each elder. You can also do it as a total surprise. Just announce in church that there will be a dinner and give date. Everyone else in the church will have already been in formed of the real event. Then when the elders arrive seat them first and then start the dinner! There can be lots of ways to do this one!