There is a false paradigm of age within lots of leadership contexts. If you are older, people younger than you are expected to give you respect because you are supposed to be smarter, wiser and more experienced. You knew it a long time ago and they don't know it yet. Trust me, I'm not saying we shouldn't learn from those who have gone before us.
If you want to grow your emerging leaders, you will need to revamp that paradigm. Instead, you will have to give them opportunities to exercise authority and responsibility and influence, in some cases, giving your leaders influence over those that are older than them.
When that happens, you'll get some feedback alright. From the emerging leaders, it will be uncomfortable, strange, and full of dissonance. Ember staff give me this feedback regularly. From the smarter, wiser, and more experienced, they will love learning from those younger than them. From the just plain older, well, you should probably just ignore their feedback.