You can book it with your planner when you have the date you want to do it. I wasn't planning to do it originally but changed my mind 2 months before the wedding. Your planner will let you know if they date you chose is available.
I use Patricia LeJeune for my hair and makeup. She came to my room at 4:30am to get me ready. She also did my hair and make up on my wedding day which was 2 days before my MK shoot.