I'm hosting Thanksgiving Dinner this year and it'll be the first time in over a decade that I'll have cooked a turkey! And never one for such a big group!

Should I cook a practice turkey? And if so, should I get the same size I'll be cooking, or is a little one enough practice?
I'm really most worried about time management and cooking being done on time. I expect we'll have about 15 adults + a few kids. That requires a pretty big turkey right?

Also, ANY tips welcomed. I haven't hosted a Thanskgiving dinner ever!