Our daughter was 4 (2002) when she reached 42" . On a typical summer day, we'd rush straight to Popeye (in bathing suits, t-shirts and water shoes) and ride as many times as they would let us without getting off. She absolutely loved the barges then. At 7, she still enjoys them, but nothing can compare to a few years ago. So, I'd guess the 5 year old would really love it and the 3 year old might not be quite tall enough.