Thanks! Sure.
About the ages, I've played with people between 20s and 30s, so I can't talk from experience. I wanted to try with my nephews but they're three and five, and I think that's definitely too young XD. However, I think the theme is kid friendly (you can judge yourself by the pictures, but I think the monsters look funny and I would've loved them as a kid xD). As for the game itself, it'd be better if they already know how to read a bit, since the all cards explain what they do and having to memorize all by the drawing can be hard.
I guess you could also try to simplify the rules for kids and remove the bonus cards and/or the circuit effects (or choose a circuit that's easy and quick to resolve like the ice one). But sorry, this explanation is becoming quite long without a clear answer ^^".
I think it can be a great game for kids that already know some board games. As the first game I'd probably go for something simpler and card based (like sushi go for instance). And as I said, if you want to play with the bonus cards, they probably need to be able to read them.
As for the number of players, I've played mostly with two, and some games with 3 and 4. I think the game works best with as many people as possible, since it increases the chaos and thus the laughs. Three can be kind of disappointing because depending on the rolls you can have turns where nobody is close enough to another to do anything besides moving.
Surprisingly, it works pretty well with two people, since it has a "special mode" where every player has two monsters. This opens the door for cooperation and combined tactics (like pushing one of your monsters forward while the other tries to delay the enemies and stuff like that), and makes for pretty fun gameplay too.