I think Kidnapped is the better book. But with your ages of kids TI might work better as a read-aloud. DON’T miss reading Kidnapped, though, it’s been one of our family’s favorite books. We all love it.
Heather, Island of the Blue Dolphins is very sad. It’s another book I love but keep it for teen years. Moby Dick is a miserable read-aloud. I read fast and it would take me approximately three years to read it aloud. OK, maybe I’m exaggerating a little. I cannot imagine reading it to a 5 and a 7yo, honestly. I only make my SENIORS read it and you couldn’t pay me enough to read it aloud, and I love above all things to read! LOL
My kids thought Swiss Family Robinson was hopelessly silly. We much preferred Robinson Crusoe. SFR is NOT a comedy book, but my kids laughed so hard through the whole thing I thought they were going to split. They wanted to find other books by the same guy on Amazon and trash them in all the reviews. I told them they couldn’t. lol.