Since fresh veggies are a staple of my Christmas dinners, my vote is for fresh vegetables always! Also - ask for help if you need it! Any trusted family members who would be of great assistance can be a great time saver. Delegating the cooking and prep work saved me when my husband and I hosted our first married - and vegan - Thanksgiving last year! It was only for eight people, not fourteen, but it sure felt like a lot of work! Not having a meat dish definitely saved time for me - no long term roasting of anything - but all of the little dishes I made took time to cook right before I served them.
And other folks' suggestions for starting early or the day before is awesome and will help you greatly too. Good luck!! You'll be great!!