We did it with Disney, and I think that's a great age, as they are still young enough to appreciate the Disney aspect. My dc is older, and she wasn't as enthralled, and while the service was great, I'm not sure the Disney premium was worth it for us. The only warning I would give you is to be realistic about how much you can see in port with a seven year old. Some of the ports are a long way from the sights (e.g., Civitavecchia is an hour and a half from Rome) and, if it's summer, it will be quite hot. After two days of walking all day, dc was ready to do a half day of sight-seeing and come back and hit the pool. That said, it's a great way to get your kid an introduction to Italy (or wherever you go) without having to move hotel rooms, catch trains, etc. Highly recommend.