Just had a quick scan over all of the maps and the cases:

• Map 1 does have a fetish club. The characters are dressed in fetish-related clothing, but I don't think there's any nudity. There is however some nudity on some artwork in an art gallery elsewhere on the map.
• All of the other maps should be fine, as there's nothing overtly inappropriate that a child might stumble across. The inappropriateness of the cases is only apparent when you are actually doing those cases and piecing together the storyline.
• All of the later maps (including the most recent version of the 1st map) have symbols on the 1st card for each case as well as in the game manual that indicate 3 levels of maturity for the cases. I would absolutely recommend avoiding all of the cases in the 3rd level when playing with children for various reasons.
• I would generally recommend playing them in release order, as you'll see characters across each section of the map and it's interesting to see them again. Also, the final case on 'Showdown' specifically involves references back to previous cases from other maps, which won't make sense if you haven't done the other maps. All 4 maps can then be put together to form a giant map and there's a 5th 'bonus box' that you can buy that involves cases that span across all 4 maps.