The Episcopal church I used to attend has done this on Christmas and Easter, and sometimes for baptisms. But not regularly. The kids are in Sunday school and come in for communion. There is very little follow through.
I've been attending a local methodist church recently where they have childrens sermons as part of the routine. It is very nice. The kids do a bible class before church.
One of the nicest childrens sermons I saw was at
Maranatha Baptist Church, in Plains GA, the home of Jimmy Carter. The pastor there really has a gift for preaching, and for connecting with the children. There are so many strangers there every Sunday, who just come to hear President Carter teach a Sunday School class for adults, and I am sure that the childrens sermon with the pastor takes people by surprise. I don;t know if they do this all the time, but when we were there it really was refreshing.