Hi Tyro,
Just a few suggestions here,
Unless your Grandson is planning on overclocking, you can tone it down and get a non-overclockable CPU, and get a cheaper or stick with the stock CPU cooler.
If you are planning on upgrading in the future and you want to stick with Intel, make sure you get atleast Haswell (LGA 1550) and not Sandy Bridge/Ivy Bridge (LGA 1155). The LGA 1155 CPU's are already outdated and the motherboard you get for them wont be able to run LGA 1550 the MotherBoard socket that seems to be going to be good for a while. So a Haswell (Core i 4xxx series) will be needed if you want to upgrade in the future without changing the motherboard.
For a GPU, why not go with AMD. AMD have got the Never Settle program on, so you get 4-5 free games with the purchase of the GPU, games like Crysis 3, Tomb Raider, Bioshock, etc. So in the end, its more bang for your buck with an AMD GPU. A Radeon 7870 is the GTX 660 equilivent or as near as you can compare, but if you have some leftover go with a Radeon 7950.
16 GB of RAM is overkill. 8 GB is more then enough. I got 8 GB's and I've never in 8 months gone over 40% RAM usage.
Apart from that, maybe get a better Keyboard/Mouse kit, and perhaps Dual Monitors instead of one. Dual Monitors are a big step over a single monitor.
Good Luck.