A good LGA 775 motherboard can be somewhat difficult to find due to age, but not impossible. Most of what's out there are micro-ATX boards which aren't that great for gaming due to thermal issues, and few support Crossfire or SLI. You also realize that, on your link, that is a synthetic benchmark which doesn't always equal real world performance? The GTX 460 is over $100 by quite a bit, so your budget is moot. For the graphics card, I would get either the HIS H685FN1GD Radeon HD 6850 1GB
or, if you have the extra cash, the PowerColor AX6870 1GBD5-2DH Radeon HD 6870 1GB
I have Skyrim and a Radeon 5850, which is roughly around the speed of those GPU's, I have the game maxed out and it runs quite well. Your kid should be fine with Skyrim if sexuality is what you're concerned about, there is none, though you can get married, none of the, ahem, benefits, come with it. Your spouse just carts around your crap, runs a store when you don't need them and fights if you want them to. Think about it, in just a few years, your kid will start asking about such things, then he'll begin driving, then asking for the curfew to be extended... They grow up so fast!