I am on WW as well....when i go to WDW, i plan all the restaurants that i want to eat at and then look at the menus prior to the trip so i will know exactly what to eat/want to eat without really looking at the menu.
For the three week long trips that i have done in disney on WW, i have lost 4lbs each.
On the cruise, you can basically get whatever you want...if its on the menu or not (and by the way, i believe they always offer a salmon dish at dinner). I also tell the head waiter what i do not want at the beginning of the trip - ie. no rice, unless brown, steamed veggies, no butter, etc. dont be afraid to tell the head waiter of any dietary restrictions or likes/dislikes you have.
Also, make sure to drink lots of water.
Here's a funny (not necessarily related to WW) - on our first cruise, the family we were dining with had a 5 year old boy. on like the 1st or 2nd night, somehow it came up (in conversation with the waiter) that the boy's favorite food is eel (imagine that!). I think to everyone's surprise, literally, for every night of the 7 night cruise, eel showed up at the table for him - there was soo much eel - if one ordered it at a sushi restaurant, it would have cost probably about 50$ for each plate!
Believe me, disney will do whatever to please you.