For the first timer it can be difficult to raise Great whites, or BB bronze just starting out. They can be really difficult to get started unless your read up on the best practices for them. Also even if you butcher earily you could have a 20 to 25 lb or larger turkey. Which is getting close to the upper limit for using normal cooking equipment.
Last years thanksgiving turkey we had a Blue slate we butchered (28 weeks) slightly earily, that came in about 12 lbs. More then enough meat for a family of 4, with left overs.
So the first question is, how many do you want to feed, and how much left overs? A 18 lb turkey will easily feed 6 adults.
If you are feeding 6 or so adults and teens a larger hearitage would work nicely.
We had all of our turkeys on grass last year and the Red Bourbon and Blue slate tasted so much better then the Great white and BB bronze in our opinion. Except when we smoked the meat, then they were about the same.
But Red Bourbon's tend to forage more, and wander further when we free ranged them.
The biggest thing with the poults is the fact they are not very smart.... they seem to lose track where they are, forget to eat or even drink when they are young... they seem to find ways to kill themselves it seems like.
The best advice I could give from my own experience is to have plenty of lights on them so they stay warm, don't let them chill or get wet as this will create a nightmare. Secondly make sure you spend a lot of time teaching them how to eat and drink.
Honestly a trick that I use for the first two weeks is something that I picked up on by losing way too many turkeys due to not figuring out how to eat/drink. The best way to teach them is to throw in about a dozen meat chickens / hundred poults. I don't know what it is but the turkey's see the chickens doing this and it's a monkey see monkey do effect. After about a week you can take them out, it really depends on how fast the poults pick this up, but a lot of the deaths in poults happen in the first 2 weeks and this is why.
After the two week period they are almost indestructable!.... Good luck.