I know you already had your potluck, but Jew Mom checking in just to clarify some things.

Shrimp is a no go.
Fish and eggs are parve. It's not meat or dairy and can go with either. So a tuna salad with mayo would be fine. You could even throw cheese into it. (Assuming you're using a vegetarian rennet.) But something like catfish would not be kosher.
Any meat would have to be kosher meat, not just not from a forbidden animal. That might be a PITA for someone who doesn't know what they're doing so just skip it.
When in doubt, go vegan is good advice.
When I decided to start practicing it took a long time to learn all the ins and outs. I would never expect someone to learn everything overnight for a potluck. I'm so touched any time anyone makes an effort. I was invited to a dinner once where the hostess told me with pride that her sweet potatoes didn't have marshmallows on them. She had found out that marshmallows are usually not kosher. (Gelatin is usually a pork product.) It was so nice of her to do! Then she served them. In a pie crust. Almost all frozen pie crusts have lard in them. I smiled and ate around it and didn't say a word. It was just nice that she cared enough to try in the first place.
