One of things we like most about Tonga is that it doesn’t seem overly concerned with tourism, it feels more like visitors need to go with the flow and accept the country as they find it. However, that doesn't mean you cannot be pleasantly surprised.
We booked our tour through email with the GM of Teta Tours which we later found out was based in Australia. We were in Tonga only for a short time and we wanted to maximise our stay by hiring a local tour guide.
We were picked up on time at 10am as agreed. We were met by Mema and introduced herself as the driver. She told us that the Tour guide is sick so she will get her daughter Taylor to "stand in" as she said speaks she better English than her. Mema's conversational skills was actually satisfactory.
We visited the Royal Palace, the Royal Tombs, the Captain Cook landing site and
eventually ending up in Anahulu Cave and the nearby beach. As we understood this mother and daughter tandem were not really professional tour guides, we praise them for the effort in answering the questions that we have. We could have visited the sites ourselves using a rented car but we think you get more value and appreciation of the culture by interacting with the locals. It will also save you time as there are lack of directional signs in the island. They also went out of their way to show us things outside of the itinerary like the famed fishing pigs.
If you compare it to the likes of Fiji where there are better tourism infrastructure and funding, you might be disappointed. But if you come in with an open mind, an understanding heart and a listening ear, we believe you might appreciate its hidden small island charm.