JakeF, Both the shops I went to this weekend recomended about a 6' fun shape for my kids. They are a about the same size and age as your kid. My 11 yr. old is totally hooked and I want to get him something other than my old performance boards to learn on. His arms got to be sore after 3 days straight of surfing.
Of all the boards my kids had when they were starting out this was the best one. Its held up great and they will still take it out when its crazy crowded. Keep in mind I make boards and my kids can have any board they want.