I am often asked about this.
I believe that children should be able to take communion if they love Jesus and understand why we celebrate the memory of this meal. I encourage them to talk to their parents about this and I also teach on this to children throughout the year. Toegther as a church family we are seeking to bring children and young people into centre of the promises we make and the practices we adhere to. This is a meal to be shared amongst all who love the Lord Jesus and lots of us can describe how passionately many children love Jesus. I have spent some time this week analysing and comparing the Bible passages where Jesus challenged his listeners about the kingdom of heaven belonging to little children and re-reading again the articles in the January 2000 edition of Theology Today, given over in entirety to the study of children.(My personal hero since entering Bible college in June 2004: Judith Gundry - Volf!)
As Stuart Murray Williams puts it: what are we saying to children if they are welcome only to watch and not to partake?
He writes a helpful set of questions here for those who wish to consider their denominational or personal position to children and communion. Please note: he does not give you an answer!
I'd also recommend "When a child asks to take communion" (by Daphne Kirk) and the excellent Grove booklet on this topic.