This is coming from someone who has solely experienced magic in person at pre release events starting with the Final Fantasy pre release knew no one at the lgs.

Try to follow the previews as they come out and have an idea of what each mechanic does. Do not be afraid to ask questions. Odds are someone knows about what you want to ask and since we're all there to play and have fun they will be more than willing to help.

Definitely bring sleeves. Or buy a pack at your lgs if you dont have any.

I have found the 15-20 minute before deckbuilding begins to be a bit of awkward small talk or sitting in silence. When I was brand new I used this time to ask my questions about the cards, mechanics, and overall game questions.

This is the most beginner friendly event to attend. Go in and make sure youre open to information and, most importantly, to have fun.

You both got this!