It can get very hot in Bobo-Dioulasso, so pack lots of water to keep your family hydrated. It's also a good idea to have either your hotel or driver call ahead to the Mosque to book a tour guide. This way you won't have to worry about choosing the right one.
Temperatures in the fall can be warm but still bearable. February through April can get to upwards of 50 degrees Celsius (122 degrees Fahrenheit), so be prepared for the heat.
December and January have cooler temperatures with minimal rainfall.