I'm really digging on SotM right now. I have a friend's copy for the moment, but I'm looking at CSI or MM to buy my own. So far they're out of stock, so I guess I may just call up my FLGSs and try to find them.
And the theme is pretty light. There is the usual villainous things, like a mad scientist trying to pull the moon out of orbit or an alien invasion, but it's very much comic-themed, which may please the kids (and kid-at-heart). One expansion has a hero that is like the Punisher in that she does guns and only guns. Not sure if that seems too dark. There is a hero named Fanatic that is kind of like a martyr paladin I guess; I haven't played that one yet. His theme is kind of religious.
I've heard good things about Forbidden Island, but I've yet to experience it.
Speaking of islands, Tobago is pretty neat. It has a unique mechanic that is technically simple but can be difficult to master. As long as cursed gold isn't too dark, it should fit in well. I don't know how it plays with 2 players, though, or if it even does.