We are doing this and have done it now for the past three years! It is amazing! Halloween is awesome and Christmas is well...magical! You will all be sure to have a blast! We arrive the 29th, go to the party on the 30th. Then, we leave on the Halloween cruise on the 31st until November 3rd. Then, it's back to WDW for Nov3-9 and Christmas party the 7th!
As for the Osborne lights, I expect to see them start the 8th. That would I believe coincide with last year. They may have started the Friday night last year, but I think it was the Saturday. We were able to get them in too!!!
Icing on the cake...Food and Wine!!!