It’s standard to tip your guide and the lodge staff at the end of your stay. Lodges usually provide a communal tip box for leaving money for the cleaning, restaurant and maintenance staff (and they will usually give some guidance on the appropriate amount to tip). People generally tip their safari guide directly at the end of their stay.
Be sure to check the child policy of lodges before you plan your stay, as many don’t accept children at all or will only allow children over a certain age. Some activities (such as gorilla tracking) also have an age limit.