We're family with 3yrs old son planning to spend our Christmas holidays in Khao Lak. We are dividing our stay between two hotels as this way we get the trip with cheaper price from the agency.
Merlin sounds quite praised in reviews, but I'm still thinking that would Laguna suit us better as it's in walking distance to centre and minimarkets and I've got an impression that also pools might be more child-friendly in Laguna.
Sunset is at the moment on top as reservation can be cancelled without charges, with Palm beach no (at least via Booking.com). In Palm Beach resort we could stay in bungalows which we cannot do in first week, idea which I personally love. But it doesn't have any pool for kids, although one review said it's suitable for children also. So we would need to spend lot of time in beach (doesn't sound bad at all, not saying that). Also we could schedule our boat trips etc. for latter week. Still wondering if I dare to make a binding reservation... According to reviews Sunset also beats Palm beach in better service. I guess both are occupied mostly by German senior citizens no so difference in that sense.