I have not been to Iceland yet so can't really answer your question, but am going in September. If you look at the Nordic Visitor website, www.nordicvisitor.com, you can look at some of their self-drive itineraries to get an idea of what sights there are on either of your two choices, and how much driving is involved each day. Their Iceland Ring Road Express, South Iceland at Leisure, or South and West Iceland tours might give you an idea of the driving times and things to see with each option. When you click on a tour, the daily itinerary is listed, with mileage. For each day, the highlights are listed on the left, which are links to the descriptions of the sights in the area. Optional Activities show things like boat trips, glacier walks, etc, that are available through tour operators. You can get an idea of how much driving is required for the Ring Road, and if your 7 year old is up for that, or where some sights are in Iceland that you don't want to miss. It's at least a start to see how much you might want to pack into each day.