I have done all 4 rooms and have been impressed by each one. This company does an incredible job at making an immersive experience in each of their rooms.
I would say 4 (adults)is the ideal size for each of these rooms.
The Cabin and Red Riding Hood are your "scariest" rooms, and they may not be best for younger children. If corpses won't bother your children, then you should be fine.
The Bigfoot room is not your traditional room escape. This is "technology" based (this doesn't mean you are logging into computers!) rather than traditional lock-breaking games. If you are claustrophobic, I'd stay away from this one (or you can wait when the path is clear).
You have unlimited hints, but the hints do not necessarily say "here is the answer." Instead they give the clues that add detail to the story. The rooms are unique as to how the clues are delivered. I also appreciate that the clues in each game are not replicas of each other. The game/puzzle creators clearly put thought into each room.
In my opinion, the rooms from easiest to difficult are:
Double Crossed, Bigfoot, The Cabin, Red Ridinghood.