Nehemiah 8:8, "So
they read in the book in the law
of God distinctly, and gave the
sense, and caused them
to understand the reading."
Notice that they spoke distinctly, gave the sense, and caused the people to understand the words. Now, how can anyone be fed if they do not even know what is said? It is incumbent upon the ministers to speak as clearly as possible. I once heard an older sister say, "Boy, he sure did some good preaching today." I asked her, "What did he preach about?" She responded, "I don't know, but didn't he sure do a fine job?" This is not preaching if folks cannot even tell you what a preacher is saying.
After being distinct in the speaking, a preacher should make every effort to define his words, make clear his points, and apply them as simply as possible (without doing injustice to the principle as a whole). My dad once used the acronym S.E.A. to explain preaching. State the subject, Explain the subject, and Apply the subject.
Finally, do it as simply as possible, and more people will understand, be made to rejoice, glorify their Father, and have spiritual edification. Then, after speaking distinctly and giving the sense, the congregation will be able to understand the word of the Lord. This goes from the children to the aged. They all feed together in the same place at the same time. Now, if the children (who are of age to learn) do not understand what the preacher says, then the preacher probably has not done a decent job at explaining things. Again, there is no need to separate anybody if the preaching is done in the correct manner.
One final point, the preacher is not the only one in this equation. The Lord MUST bless if anything is going to be accomplished. However, the congregation must prepare their ears, hearts, and minds to be receptive to the preaching. Many times, I cannot blame the preacher for my lack of blessing or understanding, for I was in the wrong spirit and inattentive. However, if the Lord is blessing, the preacher is explaining and applying, and the people are listening, we will be made to understand the word of the Lord and be lifted up together. May we ever serve Him in Spirit and in truth.