The shock loads from towing a tube/ringo can be extreme. More than you can probably realize without seeing it in person. They can break ropes easily. My point is that you need to be careful how you use them, and try not to shock load the rope/boat/tube.
Even a wakeboarder can produce around 800#'s of force. I know I sent a non stretch spectra 80ft line straight into the boat with a lot of force. Fortunately the handle was caught by someone watching, without hitting any one.
With kids the forces are minimal. An adult can pull a SIB almost in circles while wakeboarding. I can drag mine all over the place, then again I can change the direction of a comp boat. It requires full throttle just to keep it near 20mph, and I prefer to ride at 24.2mph as that is when my board comes alive. Kids won't need as much speed, so less horsepower is probably okay.
For tubes/ringos, use a stretchy rope to lessen shock loads, since the tube will not fly into the boat. For wakeboarding and kneeboarding use a non stretch rope as it will keep it from flying into the boat.
I made my own tow harness using a piece of spectra line, some stainless links, and a float. My boat also has some stainless eye bolts, although I believe most Zodiacs come with galvanized eye bolts.