What others have said, enjoy the shops and restaurants and just spending some time in the lobby area. It's a great place to sit and people watch, soak up the atmosphere, listen to the piano or the band. Mizner's Lounge is also a great place for a drink and a snack. You can also pop into Narcoossee's just for a drink if you don't have dinner plans there.

The courtyard pool is my favorite, even over the fancier pool with the waterfall and zero entry. You can even see some fireworks from the pool if you happen to be in there when the MK is having them (though now that they are stricter on pool hours, this might be harder to manage).

The marina, at one of the tables outside Gasparilla Grill, is a great place to watch the fireworks, but you want to catch the Electric Water Pageant from the beach or boat dock area. The quick service venue is open 24 hours, and a great place to stop in to pick up late night premade snacks (the grill closes at 10 or 11).

The Electric Water Pageant comes out and docks near the GF, right across the lagoon in the hollow under the monorail near the MK (visible across from Sugar Loaf/Conch Key). You might enjoy watching it come and go if you're walking the grounds at night.

Monorail to the MK, boat back. You could boat both ways, but the boat heads to the Polynesian before heading back to the MK.

The bus stop is one of the most pleasant on property, in my opinion. Bright, with plenty of bench seating. The downside is that you share buses with other resorts and are usually the last pick-up/drop-off. You might not always get a seat.