We, a family of 3, went on the afternoon tour, and there were 10 others, plus one guide for a total of 13 in our group.
The facilities are pretty limited, we had an orientation in a sort of large carport, with no restroom, although we were offered the use of one in the back of the small clothing store next door.
When we returned after our tour, soaked by a rainstorm as it turned out, there was nowhere to change except beside our car.
Our guide, Kelly, was nice, informative, patient and enthusiastic.
The equipment was satisfactory.
Be aware that if it has been raining, the hiking path to the waterfall, while not steep, is very, very slippery. There is a river crossing which could also be a challenge depending on the water level. A few of the people in our group had a lot of difficulty, one fell and hurt her ankle badly. So we didn't enjoy ourselves on the hike much, partly because we ended up waiting for the less able bodied in the group to make their way along the trail. Not that this was the fault of the organization.
The "secret" falls are nice, not very secret as there were 3 other kayak groups there when we were.
We love Kauai, enjoy nature and don't mind a physical challenge and rain (we are from the Pacific Northwest after all and used to rain), we wouldn't likely do this tour again.