A lot of CS places have fruit or carrot sticks or some other healthy option, often in place of fries. Here are some places I have found some good things at in the past:
MK - Cosmic Rays: I got a turkey wrap here that came with grapes and was really good. Noodle Station: I haven't eaten here, but I've heard of vegetarian options that would have lots of vegetables...just a thought. Harbour House: I've heard they give carrot sticks instead of fries as an option, and they have half sandwiches that come with soup or salad - not extremely healthy, but smaller portions which I know is part of WW.
MGM - Studio Catering Co.: grilled chicken wraps - if you get the kids meal, it comes with fruit as well, usually apples or apple sauce -- really yummy! MGM also has a fruit stand across from B&B theatre.
AK - fruit stands around the park
Epcot - the Land has lots of options that look better than most places, wraps, salads, etc.
I would also consider eating at mostly buffets for TS, that way you can choose which things and put less on your plate. It will be easier to watch your portions this way. I know I've read a similar thread on here before months ago that mentioned some other places, so maybe you could search and find it....otherwise, hopefully some other people will give more ideas. I think the key is just to think about it and watch what you are eating, don't overdo it just because you can!