If you can swing it and don't already have them, put slicks on your mtb. Tools have been suggested, but your kit should include a small spoke wrench. Learn how to use it and always carry it in your saddle bag. I've been carrying one for over 20 years. I've needed it twice, including just last week. If I were going on your ride, I would take two 24-oz bottles of fluids. Put water in one and an electrolyte beverage in the other. I'm older, heavier, and live in hotter environs, so you may not need it, but better safe than sorry.