Well, first of all I'm thrilled you're definitely coming here. Welcome to the family!
As for MAG/MOO, they're fairly important as far as the initial meeting of your classmates is concerned since there's a lot of bonding, but honestly don't worry about not having "a group" set up right away. Most people hang out with very different folks 2 months after MAG. You spend most of the day with your classmates every single day. The first block, which is called Foundations of the Profession, is super-easy and it's basically Vandy's way to make orientation last as long as possible. So as long as you go out with the class during Foundations and are generally a social person, you'll know most people a week in 😉 and if not I'll be your friend! 😛
For those who don't know what MAG and MOO are:
MAG is the Meet And Greet. It's the first day of orientation, and the second years (I guess that'll be my class...weird...) set it up so there's a lot of get-to-know-each-other events and games (not as lame as it sounds, for the most part), you're sorted into your advisory colleges and meet your advisors, and then those evenings there are usually dinner parties at deans' houses. You're basically officially welcomed to the Vandy fam and you get to know some people.
MOO stands for Medical Outdoor Orientation. Over the summer, you'll get a brochure with a bunch of options as far as what you'd like to do for MOO. Some of the options are: day in Nashville, day on the boat (with lots of beer), white-water rafting, paintball, hiking, and I think a few other things. So one of the last days of orientation you split up into your groups and go on your trip. At the end of the day, theoretically, you go out on a huge campout with (again) lots of drinks and s'mores and stuff. Sketchiness is supposed to ensue, and some drama begins on that evening. Unfortunately my class didn't get a campout because the universe decided to have a massive thunderstorm that evening, so instead we had a party. But hopefully the weather will be better for you guys' class.
Either way, as I mentioned, you'll meet tons of people soon enough. I know of at least one person in my class who missed MAG and MOO cause of a wedding, and it made no difference 🙂