Both of my kids learnt on El Nino's. They loved them and had good stability. My mates kids same age learnt on Star soft boards of the same size. ( maybe a local thing for WA only sorry) but they were a lot thicker and seemed to paddle a lot better than ElNino. So maybe something a bit thicker may be of interest.
The big issue my kids found with soft boards was they were a bit slow to react or turn, so often my son would triming down the line try and turn of the lip but just surf of the back of the wave.
Either way a soft board to learn is really a great idea, for safety, they tend to drag them around on the beach and kids in the water are like magnets to each other..
Either way you'll have a ball..Enjoy