We have two kids, 5 and 8. The 8-yr-old loves Settlers; the 5-yr-old loves Settlers' pieces, and builds things with them. We bend the rules somewhat when playing with kids; the Robber doesn't cause you to lose half your 7 hand of trade cards. Other than that, the only help the 8-yr-old gets is the occasional strategy lesson, and lots of experience saying things like, "You built your village on my spot! You do realize that This Means War, don't you?"

In our experience, the younger a child is, the more likely they are to want to "roleplay" boardgames and/or have different victory conditions from the adults. Playing "Monopoly Jr" and watching the 5-yr-old adamantly refuse to pay money to the owner of the space she's just landed on, because "she didn't want to go on that ride, she just wanted to watch it," or having a chess game interrupted because "the black and white pawns and the queen are going to have a tea party in this corner" are real-life examples. If the grownups (and, more importantly, any other kids playing) can stay flexible and "go with the flow" when that happens, everybody has a good time, even if you're no longer playing the game as advertised.

If you want to stick with the rules (which is equally important - one reason to play games with your kids is precisely to teach them that everybody needs to play by the same rules for the game to be fair), then be prepared for the occasional break when plans go awry. Some tears, hugs, and reiterating "It's OK when things don't go the way you wanted, so long as we're all playing together and having fun. You may lose this playing of this game, but we'll play again, and you might win that one!", and it's time to carry on.

Use the "suggested age limits" as guidelines. Play a few solo hands/games, or between grown-ups, to get a feel for the real requirements, and adjust as necessary to suit whatever kid(s) you have in mind. Be flexible and creative -- a 5-yr-old can enjoy "playing" E&T for quite a while, when their job is to sort the colored cubes and be the "bank" who hands them out and makes change when necessary while others play the actual game. The other players also get to admire the buildings and cities that the "bank" is creating while we're building our empires.

Play with your kids, early and often. Our 8-yr-old is slowly getting over the need to stop and grieve whenever things go against him, largely because he knows that he can play again, with a brand-new chance to win. I suspect he will be a much better winner (and loser!) when he's in Jr High than I was when I was that age.