Hello, if you are planning on going on an organised excursion to Marineland or the waterparks etc, may I suggest not using the ones organised by the holiday companies but by 2 companies my family and I used (including girls aged 6 & 4)
They are "No Frills tours" and "Art Tours", both considerably cheaper than the trips organised with (In my hote,l the Haiti) Thomson.
If your village does not have Brochures for these firms at reception, pop into the hotel Haiti, you will pass the hotel on the way to the beach, and take a brochure from reception.
The amount we saved for adult prices on the Marineland trip paid for one of my daughters to go for "free" compared to the thomson tours