I know what you mean, We have a scheduled gathering time that goes like this:

Announcements
Prayer
Music
Sermon
Offering/attendance
Prayer
Dismissal

We do several different things, a quick skit (involving older youth) pertaining to the lesson or giving a modern perspective on the lesson. Read a quick story, either written by us or a good book from the library. We have had the older children come up and do charades (out of a specified selections) or if possible an adult Show and Tell.

One Sunday we did Bibles, we got a 150-year-old Bible, the Pastor's first Bible, a Norwegen with a translation to English 85-year-old Bible from an immigrant grandfather, You could have hear a pin drop when we did this one. We make a request in our newsletter/bulletin and pray, this Sunday I am trying a 5-minute experiment.
I really like the Gathering Time. It sets the children in the mode to learn, gives the Area Disciples (leaders) a chance to get in the right frame of mind, offers opportunities to show a way to incorporate a lesson into real life and gets them use to sitting in a large group. Some Sundays over 100 children in one session, and yes, the latecomers don't mind joining the group when they are still in Fellowship Hall.

P. S. If they get too noises we do a rhythm clap so they know to quiet down.
1 - 2,1 2 3 We have the children repeat this clap as a sign to quiet down.

Hope you find this useful
In God's Service,
Lisa