My 10 year old son wants to play Oblivion. It will be his first real RPG, so I want him to like it but not get overwhelmed and turned off them in the future.

So I think Oblivion's basic leveling system for enemies will work for him - he won't be killed (too) much as he learns.

For mods, that leaves out OOO and others like it. But any suggestions for a 10 year old, beyond the obvious Unofficial patches? PC-wise, it's a dual-core Win 7, 6Gb RAM, 512MB Radeon 5450.

I know there are many lists out there, but I'm looking for those that would not be too much for a 10 year old first timer.

The Vanilla leveling, as you surmised, is perfect for a person new to games. As you say, he will not meet anything that he can't handle, especially if he does not level up.

I would avoid a ton of texture mods, as the video card does not have enough memory to handle those. Also, avoid the lighting mods as they tend to make things too dark and he may not want to deal with a torches at this time.

There are mods that remove or tone down the gore, so you might want to look into those if that is an issue.

Get him a nice house mod that he does not have to work for right away, this way he will have a safe base of operations until he learns the game and where to put stuff.

Honestly, I think the advice for a 10 year old new player is the same as for an advlt new player. Let your 10 year old play the vanilla game for a while before introducing mods. If you haven't experienced the vanilla game, you don't know what you want to change.