a nice car to buy would definitely be a 1/10 losi xxxnt, it's a great car (i think it would be decent for a 10 year old to learn what they are doing), it is pretty fast clocking in at around 40 mph in the rtr form. It isnt very expensive as well if you buy the rtr, around $340 and it comes with a decent JR XR2 radio. This was my first nitro car. It has been very reliable for me, and it can easily be upgraded if you desire in the future.
If it has to be a kit, then you could get the Losi xxxnt adam drake edition.