I would just take in one bike and focus on getting that one perfect with your fit session, then replicate that position across your other bikes in the comfort of your own home.
But by all means, bring in your other shoes. He has some device for duplicating cleat positions across multiple shoes.

One mistake I've made is not sitting exactly on the saddle during my fit session that I maintain while riding. Nate usually looks closely at this, but since he doesn't ride with your regularly he has to assume that you're sitting where you always sit. It's pretty easy to just jump on the bike, start spinning, and be off by a cm or more. Pay close attention to where your sitbones are when spinning. I'm not accustomed to being bolted into a fixed trainer, which also distracted me from making sure I was up on my sitbones.

Good luck. Expect great things!