Which Intel processor for this build?

Greetings everyone! I was given an early christmas present in the form of building a desktop for my 10 year old son. He has been begging me for one for the last 2 months and building computers isn't something I take lightly. However, the last computer I built was my current setup (i7-920/X58 board) and the only additions I have made in the last few years was a SSD and a Radeon 7870 so I'm a bit behind right now. Seeing as how my 5 year old i7 still kicks butt at everything, I'm willing to spend the extra cash for an Intel.

Now I've already bought the board (MSI Z77A-G45) and the video card (MSI Radeon HD7850 2GB) and I got both for $170 new which leaves me with the issue of what processor to buy. It really isn't much of an issue now (son mostly plays minecraft and watches netflix), but I'm pretty sure that won't last very long once he gets the hang of it and I can see an i7 with crossfired 7850's a couple of years down the road. So here is my issue:

An i7 for this kid is overkill right now and I'm sure I could get one for next to nothing 2-3 years down the road. An i5 would be ideal, but they are too expensive to be replaced in a couple of years. I've spotted an i3-3240 for $106 and I think that may be the best bet, but there are Pentium G-series processors for like $30-$40 cheaper and they seem to be similar to i3's performance wise. So should I get the i5 and not worry about an i7 in the future? Would an i3 be the best bang for the buck in the meantime or would a much cheaper Pentium do the same job?

I wouldn't go any lower than that i3 if he will eventually be stretching his legs on it and personally I would look for a quad core (if that isn't one, I am not sure).

If you want to be able to overclock though, you need to look at the "K" series processors... i5 3570K.

I think that i3 you spec-ed would be perfect. I put a very similar one (i3-3225) in one for a family member (only difference being slightly better graphics because I wasn't putting a dedicated card in that one) and with the hyperthreading, it's awesome. For every day use, it might as well be a quad core. And I don't even have an SSD in that one, just a Blue drive. Blazing fast for the light load it has to endure.

Then, you're not in too much money, and later on down the road when you want to throw a 3770K in it, you can take that i3 and use it as a file server or hand it down to another family member for light home office duty or the like.

Yeah, I was thinking the i3 would be best. It seems to be a very capable processor for only being a dual core and the price I would be paying for an i3-3240 plus the board itself is less than the AMD FX-4xxx alternative, but will give him lots more room for future upgrades.