Answer
We think that the FG800 would be the perfect starter guitar (and one that should last many, many years thanks to its solid spruce top and high level of craftsmanship). Many of our customers have bought this model (and its predecessor, the FG700) for their children around the same age who've then continued to play them as adults.
Whilst smaller Yamaha guitars are available (for instance the smaller-bodied FS800 and the 3/4 size JR Series), at that age, playing a full size acoustic is usually manageable and ensures the player grows into playing a full size instrument.