Tips on cooking Christmas dinner for large group
We did the best turkey ever on Thanksgiving. Butterflying was the key http://www.seriouseats.com/recipes/2012/11/butterfiled-roast-turkey-with-gravy-recipe.html. 

It cuts down massively on oven time, tastes great, was fun to prepare with my son.

The oven is fairly hot, which is better for doing potatoes etc at the same time. You can do oven potatoes in the skin: no foil, just poke the potatoes with a fork a few time and rub olive oil on the skin, 45 minutes or so at 425. It also makes the turkey very easy to carve, so that's faster and a lot less messy when dinner time comes.

If you do potatoes and turkey in the oven, you have still the whole stop top for the rest, so perhaps you should choose dishes that not need an oven.