We've stayed there once (bucket list item) and LOVED it -- I am so excited for you!
I'd check out the Tikiman pages website about the Polynesian, and consult the map, to decide what building to request, particularly in light of your likely desire to be in an accessible room near an elevator (or on the ground floor), and near transportation. Be sure to call or fax Disney with your room requests/needs ahead of time, and be ready to politely renew those requests at check-in if they haven't been met.
We were in a DVC studio in Moorea when we were there, which if you're looking at a map appears to be far from the Grand Ceremonial House, but in reality, it was only about a 6-8 minute stroll away, since the resort isn't all that spread out. We didn't have a lagoon view (instead it was a view of lush greenery and a walking path) but we loved it! It also put us a little closer to the TTC, which was handy when we wanted to hop the monorail to Epcot (rather than the MK/resort monorail, which you can board at the Grand Ceremonial house).
We didn't eat at Kona Cafe, but we did do dinner at 'Ohana (ADRs right at 180 days are generally required) and lunch at the excellent onsite CS, Captain Cook's (as well as a breakfast of Tonga Toast which we took back to the room with us, from Captain Cook's -- it's the same as that served in Kona Cafe), and they were very good. If you have a chance to duck into Trader Sam's for some fun drinks (take note of their hours and if possible, be ready and waiting outside when they open for the day so you don't have to wait for a seat), it's a neat place, too.
We haven't been in December, so I'm afraid I can't weigh in on the holiday offerings, although there are sure to be special decorations and themed activities going on.
Have a wonderful time!