Tbh every time i've been to american (been orlando twice and vegas) I didn't eat much lol maybe it was the excitement or the heat. The way I see it, eat sensibly as you would if you were going on hols in england. It's not a completely different world! Go for what you KNOW are healthier options... but remember u are on your holiday!! I would recommend that US eating out guide, sounds great (i mean purely because portion sizes are very ...different lol even for places like mcdonalds!).
WWs is american too so im sure that u can pick up WW bits on the go from Walgreens etc...
Above all have an amazing holiday!
PS. Would recommend, tho its probably a gazillion points, but if you go to Downtown Disney theres a place called Earl of Sandwich and they are to die for! I went to the one if Vegas and it was heaven!xx