How friendly is this game to play with bright but pre-literate children?

The game is pretty language independant, being mostly composed of pictures and counting to ten, but some of the decision making can be super tense. Also, the game is not what I'd call easy, so you might want to find a way to either make it easy for them or prepare them for repeated failure. I guess the real question is how good are their imaginations? The real joy of the game for me isn't even in the winning, but in thinking about my gnome running around this sub, half-drunk, fighting his way through flooded rooms, putting out fires, and working on a nuclear reactor to save the day. Ooh, that brings up another point, how ok are you with this game's portrayal of alcohol usage for the kiddos? They call it grog, which is a little safer than vodka, but it's still a theme. Anyway, hope that helps. Let me know if you have more specific questions.

We're talking about the 3yo - 5yo range here?

I think it would be a dicey thing. A lot of the game is about prioritizing which of a half dozen crises you're going to work on which will require a fair amount of focus and attention. If they can sit and focus for 40 minutes they'll do fine. Take your best guess as to how fidgety they are. The actual mechanics are pretty simple, if they do well with other board games I wouldn't worry about that.

The difficulty is very easily adjustable as well, the goal is to survive for X minutes until resuce arrives, but you could adjust X to be whatever number makes for a good close game for the kids.

If you are looking for a game to play with the youngster look into Wings of War, they have a simple set of rules that 5 year olds can play (really I have played it with 5 year olds) and if you want to get more complex with your friends there are optional rules to make it more complex.

I have played the game a few times with my 6 year old. English is not his first language but learning the cards didn't take him long. You can even play the game as a two player game to learn your kid the game and since it is a cooperative game giving suggestions won't be any problem. After one or two games my boy was able to explain the rules to another adult that hadn't tried the game before. I see no good reason not to try it with your kid!