Although I cannot ‘recommend’ this unit having never used a metal detector in my life – it would appear ideal for a 7 year old. Looking at the spec – it has a limited performance, only detecting metal down to around 2 inches or so, but then you don’t want little Johnny digging down to Australia looking for buried treasure.
If in 6 months time, Johnny cannot be separated from the device, you could consider investing in a better model, otherwise put it away under the stairs never to be used again.
http://www.maplin.co....e.aspx?ModuleNo=27591