You want a low-wattage bulb so exposure times are long - especially true if you are using enlarging paper.
A 7 1/2 watt round bulb was the usual size.
As far as chemicals in the bathtub - the chemicals used to clean the bathtub are the dangerous ones. Tell mom and dad that developer is pretty much coffee with washing soda, stop bath is vinegar, and fixer is the stuff used to dechlorinate water in swimming pools in case someone overdoes it with the chlorine bottle. B&W photo chemicals are some of the safest chemicals in the house.