My wife did her open water certification dives in Little Cayman and I would not hesitate to take a new diver there or recommend it to a new diver. The deepest walls start in 15 or 20 feet of water, so there is always something great to see in a depth you are comfortable with. The max depth they will permit (under Cayman Islands Watersports Association rules) is 100 feet and you don't need to do that. There are only a couple of sites, like Randy's Gazebo, where there is something in particular to see at 90-100 feet. At Randy's Gazebo, there is an interesting coral formation shaped like, well, a gazebo. Truth be known, you wouldn't be missing that much if you didn't see it. Stay in shallower water if you want, see the rest of the reef and the critters.
One skill you will need that you don't use in Cozumel, but probably do use in Bonaire, is navigation. The Little Cayman dive ops usually do not conduct guided dives. They give you a good briefing and declare the pool open. It is up to you to plan your dive (including figuring out turn time and turn pressure), navigate out, and navigate back. There generally is a DM in the water and he or she will give you a tour if you want, but you have to ask. Navigation is usually not too difficult, but it is something you have to do.
Don't worry about it, Little Cayman diving is easy and fantastic. You will love it. It pretty much spoils you for everything else.