Solo, for
MNSSHP I prefer a quiet dinner at one of the monorail resorts - perhaps at the Concourse Steakhouse at the Contemporary or Kona at the Poly. Then I take the monorail to the park and walk in as it all begins; the lines are a bit longer that way but you do get the experience of walking in and experiencing all the Halloween magic the way it's "meant" to be seen.
For the Magic Kingdom in general, Liberty Tree Tavern at lunch (it's a character dinner at night) and The Plaza for lunch or dinner are great choices. They both offer lighter choices and are reasonably priced sit-down meals. For instance, a burger at either of them is only a couple of bucks more than fast food, but you get to sit in a wonderfully themed, air conditioned, (relatively) quiet and relaxed atmosphere. Both are really excellent choices for solo dining.
At Epcot, Le Cellier is always a nice choice. Either for sandwiches at lunch or steaks at dinner, it's a really nice place to rest and get away from the bustle of the parks. I also enjoy the sit-down in Mexico, as it overlooks the ride - but I usually just have a couple of appetizers instead of ordering a full meal. Since you are solo and on your own time frame, you may want to "pick" your way through World Showcase; it sounds like you will be going during the Food and Wine fest, and you can easily go from country to country sampling bits from here and there. You can try some of the cheese soup at the Candian pavillion (not my cup of tea, but people rave over it), some sausage from Germany, a desert pastry from Norway. Pick your way across.
Good luck, and happy birthday!
NED
PS - Check out the Solo forum for more great tips