NCL Cayo Levantado beach excursion- how soon can you tender back to ship?

The excursion is listed as 5 hours, but are tenders continuously running back and forth to the ship? We are traveling with a couple of small kids and 5 hours might be too long for them in the sun.

We took a tender back at 3:00 PM and I'm not sure if it was the first one back or not. They would not run the tender back until enough people showed up to fill the tender... so this early you might have to wait 20-30 minutes depending on how quickly it fills up.

There is shade available on the beach further back from the water. This is a great beach. Very calm, clear water.