Think of Africa, and somehow helping people always pops into most people's mind. There's a lot of controversy surrounding visiting orphanages during your travels, but the fact is it's a evil necessity for the orphanage. Most people who choose to visit an orphanage will either provide a donation of cash, clothing or food upon arrival, sponsor a child once they return home, help give the orphanage PR through word-of-mouth or end up returning to volunteer.
This is probably one of the "richer" orphanages in Arusha (Usa River is about 45 min drive from Arusha). It's run under the Lutheran mission, but there is certainly no obvious sign of this there. Upon arriving the guard at the gate will take you through to reception and you will be met either by the Director or Manager of that shift. Many volunteer projects incorporate this on their offerings so you will see many volunteers there helping out either short or long term.
Be warned, this is filled with lots of toddlers and within a few moments of entering expect to have a child on each leg and perhaps on each hip! They are adorable but yes it is heart-breaking. Don't be mistaken, these are not all orphaned, in fact the majority perhaps lost one of their parents and the other parent can't afford to raise the child at this expensive age of baby formulas, nappies, medicine etc.
Call or email in advance and find out the latest feeding hours - they love you helping to feed, change nappies, and play before and after sleep time.