Visiting Maputo/Mozambique with Sertorio was a great decision in our trip.
I am not going to comment on the Maputo city itself as this is something you can find in other reviews or websites, but will focus on Sertorio.
Sertorio's own story is completely integrated with Mozambique and South Africa recent histories, so spending the day with him was an incredible history class.
Mozambique is a country that has just recently got independent (around the 70s). When the portuguese left, they took with them all the doctors, engineers and teachers with them so the country was left with nothing. To reconstruct the country, the local governement invited Sertorio to be an english teacher there. He went there and not only gave students classes, but was continuosly enhancing his craft by studying in the UK and US to bring the best stuff to this new African country. During his years in Mozambique, he also helped in the fight against the apartheid, so he not only made a difference in reconstructing Mozambique, but got to change South Africa's too!
This is just a brief of everything you can learn with Sertorio...
Strongly recommend visiting Maputo with him if you intend to visit Mozambique from South Africa.