I spent a great two weeks exploring the southern coast and really enjoyed it. In Kilwa Masoko I stayed at the New Mjaka Enterprises Hotel. It was a good value at 15,000 shillings for an en suite room. Running water was brackish and sporadic, but a large collection barrel ensured I was never without. The mattress on the bed was getting really thin, but the staff was super-friendly, and I spent hours talking with them in broken Swahili.
The map on page 544 shows the New Mjaka on the same road as the Kilwa Ruins Lodge. It is actually on a lower road that is not pictured. Heading south from Kilwa ruins you will come to a large metal observation tower. Almost directly across from this is where the correct road forks off. Take this fork, and about 10 minutes later you will see the New Mjaka on your right.
I would have loved to dine with the family at New Mjaka, but they only cooked enough food for themselves. I probably could have given them some money earlier in the day and had them shop for me. As it was, I had a great buffet at Kilwa Ruins. At 20,000 shillings it was not cheap by TZ standards, but there were tons of different options, from chicken to fish to octopus. The cream of chicken soup was especially delicious.