I have my excursion form from the 4 night that I took in September 2001. It states that the children pricing is from ages 3-9. I assume that the 17 month old would not be charged for the excursion.
You are making a great choice with the ages of your kids. There are places there to relax and have some great family fun. The lagoon is a great place for little ones to play in the water. I enjoyed the hammocks and the atmosphere there.
Vicki