Hey there!
My husband is also pescetarian, and I'm a vegan. I'm pretty sure no matter where you go, you're going to have something delicious to eat and everyone here has offered some really great suggestions you can't go wrong with.
For my upcoming trip in November, I have ADR's for Crystal Palace (character buffet with lots of veggie options), Boma (african buffet), Tusker House (another buffet, inside the AK), Sci-Fi Diner (they had a tofu dish that looks amazing), California Grill and 'Ohana. For counter services, I've heard great things about the Columbia Harbor House in the Magic Kingdom (if you like shrimp, they have some great breaded shrimp and a veggie sandwich, as well as veggie chili), Sunshine Seasons in Epcot and Tangerine Cafe, which is also in Epcot.
Look into Sanaa, too, which is at Kidani Village. That's one of the newer African restaurants and I've heard great things about their veggie options.
Cat Cora's new restaurant Kouzinna also seemed to have quite a few vegetarian options on the menu but it's so new that I don't know too much about that one yet.
Good luck, have fun!