I'm a teacher, among other things. My goal is to get my students out of my class to the next level. I can teach them something, impart knowledge about something- but they must learn how to use that knowledge,  otherwise they become hearers only and not doers. Preaching and teaching are there to equip the Saints to do the work of the ministry. We minister to the immature in order that they might mature.  We do not replace the Holy Spirit in their lives - we do not do His work for Him. We are not to stunt a child's growth, keeping them dependant on us, feeding them milk and never meat. It is by reason of use that their spiritual senses are exercised, which molds them into healthy Saints.

Example: I try to maintain a clean classrooms.  If I see garbage on the floor,  I can pick it up or I can have my students do it - so they can learn by doing what it is I expect of them. I can tell them how to pronounce English correctly but until they DO IT themselves they haven't really learned it.

I can do all the teaching in church, all the prophecying, all the praying, laying on of hands for healing, or, I can demonstrate these ministries, then release the people to do the work of the ministry  "For the perfecting of the Saints, for the work of the ministry, for the edifying of the Body of Christ....." remember, the body will grow healthy when "every joint supplies, according to the effectual working in the measure of EVERY PART, maketh increase of the Body unto the edifying of itself in love".

Trust the Holy Spirit. He knows what he's doing.  As the Saints are allowed to minister to one another,  it will quickly become apparent where their talents lie, what anointing God has chosen for them. Their state of maturity will quickly become apparent also, and age has nothing to do with it.