{....had to go dig through my DS's (7) pile of board games....}
1. Blokus...fit the different shaped pieces into the game board. Comes in many variations, including a nifty travel one.
2. Monopoly...I know it's an old stand-by, but my DS loves it. Great counting and strategy skills...He is quite good at it, and has a hard time finding suckers (I mean people) who will play with him. (It's embarrassing getting thumped that badly by a 7 year old

)
3. Yahtzee...again, it's been around forever, but great for developing math skills. The 4 year old can help play too. (counting up the groups of numbers, for example.)
4. Trouble...very simple game, more fun the more people you have (max of 4). No great skill involved, might be a good one to play with the younger child.
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5. Carcassonne...this one is a little bit more difficult, not for the younger child at all. It is a tile laying game, you try to complete the little roadways and put your counters on the tiles that will get you the most point. It's the first "serious" game that my son has taken a real shine to. You don't have to play with all of the really complicated rules, so its definitely playable for kids.
And if all else fails, there is a wonderful website called boardgamegeek.com, which is exactly what it sounds like

. They have a thing called GeekLists...type in 7 year old boy, and you'll get lists of games people have put together....
Okay, I'm going to take my geeky game self away now

...Have a Disney day!