Just to say, I would really recommend getting the kids in the darkroom. A lot of the fun of this type of activity is seeing the photos appear, especially if not everyone's pinhole images will make the cut.
For this you need a safe light but see if you can get one free/cheap second hand, or as suggested borrow one.
You will need to do a few tests to find the right exposure at both stages of the process.
A cheap vinegar stop bath will cut your stop time from 2-3min to 30 seconds. RC paper will drip dry in an hour or two, or a few seconds under a hair dryer if time is really short. This could save a wait after creating the negatives.
Get larger trays so you can develop several images at a time. Garden seed trays may be a good alternative.
Strong fixer i.e 1:4 strength will speed up fix and wash times.
You shouldn't need a breathing mask, I find vinegar stop he most unpleasant smell. Developer and fixer have never bothered me.
Check your local regulations but most photo chemistry can go down the drain in these small quantities. This is not the case if you are on a septic tank.