Ran the GC last July / August in a kayak, with a private raft group. I would gently suggest that you think hard about taking a 7 year old along. And I'm normally all for exposing kids to some risk at an early age, but there are some special circumstances around the GC. For starters, the water is really cold; 48F to 52F. That time of year, they're trying to produce maximum electric power during the day, so the water fluctuates from 9000 cfs to 17,000 cfs, daily. While it's not technically demanding, 17k produces some spectacular wave trains and holes. Any swimmer is going to be in for a long ride. We had several people in the water (out of 4 rafts) and they all took really long, really cold, really scary swims, even with two kayaks to pull them to shore.
I really hate it when someone comes along with a FUD message like this, but I just wanted to share my recent experience and let you know what you're in for. (Maybe he could walk the Class 8, 9's?)