I'm allergic to tree nuts, a frequent travelling companion is allergic to wheat, and is lactose intolerant.
We have had incredibly good experiences at WDW restaurants. The only times we've "called ahead" are to the Italian places for rice pasta (48 hours notice) and Hoop De Doo Review (they made my friend the same meal only without sauces, and served her a GIANT fresh fruit paltter in lieu of the shortcake for dessert.
I always tell the server as soon as I sit down that I have food allergies and need to speak to the chef, and then verify that my selections are nut free, nuy oil free, and not made on equipment that proceeses food that contains nuts. (big problem for me!)
I have never had any probelms, and they've gone out of their way to make substitutions as needed, including putting together combinations not offered on the menu and cooking things differently or without sauces.
Just as an FYI, all foods that are cooked in oils at WDW are cooked in canola oil unless specified differently on the menu. The baking powder bisquits served at many of the restaurants at breakfast are made by Pillsbury and shippe din frozen, and are nut free.
Back to your original question. Toaster ovens are a fire hazard in hotel rooms. There is not a safe place to put one to use it (heat resistant counter top, etc.) If you really want to go the "cook it yourself" route, then the home away from hoems are your best option. You might want to think about renting points from a DVC member, it will save you a bundle.
Anne