I have 3 kids. 10, 7, and 5.
My 10 year old has no interest what so ever. We let him pick a fish but once it was in the tank he was done, if he can't play with it on his tablet it doesn't interest him. I expected this because he could really careless about our dogs as well.
My 7 year is a different story. She feeds most days, the fish and the dogs. She likes picking coral because the are pretty and always helps my wife feed the coral. She also has been taught how and can spot feed coral like nems and plates and I have no fear in her doing so.
My 5 year old is opposite of both of them. She picked a fish and loves watching them and the coral move. She has no interest in feeding but loves the excitement of watching feeding time. However, if the stand is open and my hands are in it you can guarantee she's sitting on the floor next to me watching and helping. She knows what every switch on the boards do, when and how to turn off things for feeding and maintenance. I bet she could do a WC at this point if I needed her to.
The tanks are my hobby, my wife got me into fish keeping as a stress reliever (I'm sure she never thought it would turn into what it has), but my family is very much involved and they are involved in what they like. Makes it more enjoyable for everyone. My 2 learn by asking and watching. If I sat them down with a book they would loose all interest in 2 minutes. But seeing and doing is a whole different thing. Good luck. Let us know what you find and what works for you.