Firstly, if the plot of this show appeals to you or your kids at all, please, please read the book before finishing it!!! It is well-written and thoughtful while still managing to be even more humorous, clever, and suspenseful than the show is.
Review: The child actors are lovely and the costumes impeccable. The first two episodes were wonderful and really got my hopes up. However, the scriptwriters subsequently made a lot of confusing choices in adapting the story. (I've noticed that a lot of the 5-star reviews from fans of the books were written after only the first 2 episodes.)
Of course some things have to change when going from page to screen, but the show takes a lot of liberties that don't actually benefit the storytelling in the show anyway. It's odd. As just one example out of many, there is all this added drama/scheming amongst the adults while the kids are on the island (the book is solely from the kids' perspective). Some added plot gimmicks to give the adult characters things to do would be fine if they didn't exist at the expense of having time to better develop the kids' personalities and relationships. But unfortunately they do, so the development suffers and the kids' relationships are lackluster and rushed.
It's quite frustrating to know the potential and then see the show undermine itself this way, and I'm not sure I'll finish it. But if you haven't read the books, I could see the show being very enjoyable for what it is. Hence the 3 stars instead of 2.