TL;DR: Great for families, beginners, and couples. It's a unique experience.
My husband and I did the kayaking tour through the Mangrove Tunnels, specifically with Sea Life Kayak Adventures. There are many kayak and standing boat companies that do tours in these areas, but there's a lot of tunnels and ocean to cover, so we only ran into other tours twice.
We saw lots of wildlife from birds to crabs to invasive jellyfish. No manatees sadly, but we did go out when the tide was really low, so we saw more fish and small underwater animals. They said manatees are more common during higher tide around winter when the surrounding waters get cold. Do your research if you want to increase your odds of seeing one.
The tour guide was fantastic. He was funny and very knowledgeable about the local wildlife and mangroves, despite only living here for a couple months. The only downside was trying to hear him. We had to stay at max two kayaks away if we wanted to hear him.
Our group was sort of small, maybe 10 people total. A couple pre-teens, but the rest were adults. This tour is great for beginners, but at the same time sucks for beginners. It's common to bump people with your kayak if you don't space yourself out well, but we also had people get stuck in the tunnels, which caused a chain reaction of everyone getting stuck if they don't stop in time. The tour isn't rushed, so we had time to get everyone unstuck. It only happened once though, but my tip to beginners is to take things slow and not panic if you bump something or get stuck.