I don't know about having a busy day on day 1....My advice would be to try and cut out some activities today and attend to you physical needs of rest and hydration. If you can't get out of the responsibilities...hydrate as much as you can throughout the day. Be prepared to have probably a restless sleep tonight but KNOW this will pass after a few days and you will be grateful you stopped. The first time I stopped I was 41 also and maintained 8 years of sobriety. You seem in the same mindset I was in...READY.
And I wish you the best in this effort to live your life not focused on escaping with alcohol.