I have done a GG twice. Once as a
DVC member and once not. Our first trip we stayed at WL (not villas). Our rooms were supposed to be adjoining and were not. I know this isn't promised but it doesn't seem that hard to make happen. We had to wait until the following day, change rooms, to have connecting. On that same trip, we did the Safari and dinner. It was great, dinner was family style at Tusker House. Safari was much, much better than regular safari--not silly baby elephant story. It was also a 20-30 minute or so ride. We were not offered preferred viewing for fireworks or parades. No special treatment for dining ressies either.
Our second trip, as DVC members, was pretty much the same--except this time, we were not even in the same section at SSR! It took over 1 hour to get everything figured out--a total waste of time IMHO. We did not book a GG experience on this trip. I did it solely with the hope that our rooms would be in the same building--eventually there were --but at the expense of my time.
If it were me, I would not book a GG again. I would just deal with the hassel at check in to get our rooms together. Has not worked for me yet. Also, the Fireworks cruise that was once offered for MK viewing is not offered to all guests. The Illuminations Dessert and Fireworks viewing sounds nice but personally, I have been enough to know where to get a good viewing spot, and thanks, but I'll bring my own dessert from Kringla Bakery! Breakfast with Mickey at Tony's in MK sounds pretty cool but I can not comment on that experience. If I had two days at MK I might consider this but I would not want my only MK morning to start after a long breakfast while the crowds filter in.
Good luck with your decision.