At 8+10 years old, my children still like object lessons.
Object lessons are Bible stories and deeper concepts taught by something real they can see. Jesus used parables or stories with several layers of meanings. And so realia, or real tangible objects, help to express ideas and character qualities to everyone – not just the younger set.
Here’s some links I’ve wandered across lately:
http://www.sermons4kids.com/ – check out sermon index – OT, NZ, powerpoint, etc
I’ll add more as I stumble across them …