Hi,
I'd like to give you a proposal for your query.
To be honest I think it is almost an impossible job to get what you ask for, if you want to keep it simple. And I like simple.
Although there might be a great FUN way of getting what you want in a slightly different way.
I don't know if you ever heard of Room Size Pinhole Cameras. What this means is that you make of any room a camera obscura, by darkening the windows and hereby the complete room with black plastic and the use of gaffer tape. You shut out the daylight by sticking the black plastic over all the windows that the room in question has. This by itself is a really fun way of getting your kids involved in the most basic way of photography.
Second step is to determine where to make a hole the size of a quarter in the plastic and most centered in the room so light get as equally divided as possible on the walls, floor and ceiling.
Shut down the artificial light and wait untill your eyes are adapted to the darkness, and you start seeing the external world appearing on all the surfaces in the room.
Next you look for the nicest place in the room to make a long exposure photo with either a digital camera or in your case an analogue camera with ordinary film. Good tip is to use ( if you have one ) the digital camera as a reference or check up for the right exposure. Position your camera in the room and shoot the room.
What your about to get is really amazing, your kids will be trilled !
Depending on which film you shoot ( b/w in yr case ) develop the film as usual and make these prints afterwards in the dark room with your kids. This way they are witnessing not only the appearing on the photographic paper, but have been really actively involved in this wonderful process. I'm sure they'll love it ! Happy Pinhole Photography !
Kind regards,
Luc.