Dead Man's Doubloons
Three to ten players? Bummer. It's usually just my wife and I, these days.
FYI, we just implemented 2 player cooperative rules - it's available an optional variant, as it really is different from the 3+ player game where there's a hidden loyalty / adversarial aspect, but we found the 2 player version to be quite enjoyable. Hopefully you and your wife will like it too!
You can get the updated rulebook and other resources here: http://geroex.com/mars-vs-earth