Lots of kids are so used to the "gotta win" mentality (since it is very widespread in today's society) - I like playing co-op games. Castle Panic and Forbidden Island are both good co-op games that are very suitable for young kids/family. Castle Panic also has a "master slayer" rule, but you don't have to use it.
Speaking of co-op, I just got Defenders of the Realm yesterday. Co-op for 1-4 players, you have to travel the land and defeat 4 invading Generals and their minion armies, while protecting the home city and keeping the land from being tainted. Shares a few mechanics with Pandemic (and probably other games) with the Overrun/Taint of areas (similar to Outbreak in Pandemic) but the game as a whole feels entirely different to me. It feels like a game, and is much more immersive, versus feeling like a puzzle.
The setup notes are little confusing, but not too bad. Unfortunately, we started playing late last night and my wife postponed the game (we were able to beat Varkalak right before we quit). I'm only half a game into it, but so far I like it - the instruction book is something like 16 pages, but the game is actually pretty easy to learn once you get into playing it. It has a pandemic feel, with the overruns of minions, but while I didn't like Pandemic, I like this one much better. Maybe the theme, maybe the fact that my paladin with a horse figure is racing toward the space with three Minions and a giant dragon, instead of just cubes. There's more options in a turn and all the fantasy trappings (we've tried three quests, failed two of them,and I'm going to go for another one while I still have time) help make it a more engaging/immersive game to me.
There's definitely luck - things can happen real slow or real quick based on the cards drawn (the generals have only moved a total of 4 spaces, and Sapphire the dragon hasn't moved at all), and a poor dice roll can hurt - but there's enough balance (so far) that it doesn't seem overwhelming. Plus the risk/reward ratio for the quests seems fair - the one I'm going for now lets me move as if on a horse (which doesn't matter, since I'm the Paladin and can do that anyway), but gives one reroll of all failed dice every combat.
1-4 players, 8 characters to choose from, the designer has already released multiple P&P scenarios/variants, there's 2 boxed expansions out already (one with just a new character, one with new enemies, minions, cards, etc). Says 13 and up, but if a younger one has someone to teach the game, I think younger kids could play it (for some reason the rules as written just didn't click in my head, until we got a few turns in then everything cleared up). Playing time on the box says 90 minutes, I can't refute or validate that yet.
If you're looking for co-op fantasy with an 'epic' feel definitely check out Defenders of the Realm. It feels more 'epic than Castle Ravenloft, for example - due, I'm sure, to the theming of being outside in this fantasy land and having to travel around to fend off the invading generals and their minions, versus exploring narrow paths in a dungeon filled with monsters. Takes up about the same amount of table space, but is easier to set up.