Hi. My sister and I are also vegetarians and we were in disney in august. I'll tell you some places that we ate, and LOVED!
fifties prime time cafe in MGM has peppers stuffed with rice, veggies, and a mozzerella cheese, sitting on a bed of mashed potatos. My sister and I loved this dish so much that when we came home I tried to make it as a recipe. This dish is sooo good.
also in MGM is Hollywood and Vine. This is a buffet style place and I think their menu changes every once in a while, but when I went they had these things that were vegetarian:
mashed potatos
tomato and buffalo mozzarella salad
cucumber salad
vegetable lo mein
sweetpotatos in a rootbeer sauce
corn w/ veggies
other types of salads
DESSERT!! =)
At spoodles on the Boardwalk they have a GREAT meal for vegetarians (although spoodles is a bit more expensive than the others). It's two stuffed spanish red peppers, stuffed with veggies, chick peas, and a hummous type sauce, on a bed of fancy rice... this meal was really good as well.
Rain forest cafe (either in Animal Kingdom or Downtown Disney) has a few great vegetarian meals including a flavorful veggie burger, a portobello mushroom burger, different styles of pizzas, and a pasta dish.
Planet hollywood (down town disney) also has a few veggie selections, The parmesean spinach dip is really good, so is the bruschetta (for appetizers). for a main course they have a mushroom burger and a pasta dish that is veg. among other selections that I have not tried.
In the Animal Kingdom Tusker house which is more of a 'fast food' type service, there is an excellent veggie sandwich on big foccacia bread. (not too expensive, only about 8 dollars for this and a drink)
In the magic kingdom another fast food type service is the Columbia Harbor house they have a great sandwich called the coral reef sandwich, which has hummous and a slaw of cucumbers carrots and other veggies. (priced about the same as tusker house)
In Epcot at the land food court they have TONS of veggie foods, they have a great Veggie lasagna, a veggie wrap, etc.
Most everywhere in the parks and resorts they have french fries, and some sort of veggie meal. My sister and I were big fans of the grilled cheese and fries @ the all star resorts. I hope these help, there's atleast one in each park for you there. Have a great trip!
tricia