For 125, you want electric roasters, not crock pots; each holds enough for 50-60. And yes, most people use "hot pot cooker" as an alternative to crock pot cooker; some have more temp control than traditional hot pots.
I allow 2 tables per each 25, this might vary a bit depending on the menu. I set up the desserts and beverages together separately. I have an article up on laying out a buffet:
Yes you can cook turkey ahead, cool, slice, freeze in thinnish layers foil wrapped. Transport in ice chests. Thaw refrigerated. See the Reheating turkey safely article for storage and reheating help.
If I were making the turkeys, I would make 9-10 gallons of turkey soup also, freeze and reheat for one of the meals.
I might also make 9-10 gallons of my beefy tomato vegetable soup and freeze for another meal. Triple recipe: