I've used VC RC paper as pinholes and in my experience they benefit from taping a multigrade filter behind the pinhole to reduce contrast, however it still works fine without it. For your project I'd be inclined to get a box of 100 of whatever's the cheapest RC paper (VC or graded.. if graded make it G2 rather than G3) as you're not going to have the time or filters to start playing with that aspect anyway.

For handmade pinholes, you need to test/measure the hole size and use the focal length of your camera to work out the working aperture to calculate exposure times for the slow (roughly ISO4) paper. You might get 15sec exposures with film, but paper will be more like 2-3minutes, maybe longer depending on light (of course!). I measure my pinholes by projecting them in my enlarger and measuring then calculating based on enlargement factor, but you can do something similar by scanning them on a flatbed scanner and doing some pixel measuring and math. Alternatively, test them in the field, although if you're using different containers as the 'camera', each combo to be used will need testing.

Other random thoughts...

Get a safelight so the kids can watch the developing... that's a definite 'wow' part of the process.
You can develop multiple sheets at once, just keep them moving in the developer (and stop, fix & wash)
An un-filtered VC paper is generally approx 2->2.5 grade equivalent
Paper comes in different surfaces (usually gloss levels). I've always used a low sheen (Ilford Satin or Pearl, Agfa Semi-matt), not sure if that's a recommendation or maybe someone will suggest to use 'Gloss' for some reason. I personally don't like gloss for anything so maybe I'm biased