My advice is to get a sampler platter for everyone to eat off of and just take what looks good to you.
Some sushi basics, though:
Maguro: Tuna. A red tuna that is generally mild and delicious. I think it's usually bluefin tuna. There might be another kind of Tuna on the menu called "Toro" - It will be a little more expensive, but it's worth it. A fattier cut from the belly.
Sake: Salmon. Usually smoked, I believe. Orange with white streaks though it. Nothing surprising here, you've probably had salmon before.
Hamachi: Yellowtail. A white fish that tastes a little more fishy.
Saba: Mackeral. Silver/blue skinned whitefish that is a little less fishy than yellowtail.
Unagi: Eel. My favourite. Broiled and brown. Usually covered in "Unagi sauce" whatever that may be. It's light and buttery and falls apart in your mouth. A safe bet if you're afraid of raw things.
Ebi: Shrimp
Tako: Octopus. Often overcooked and sliced too large. If you get a nice cook and cut it won't be rubbery. Subtle taste.
Kani: Crab. Often imitation crab is used, called crabstick or Kani Kama. If it's in a roll, you'll likely not notice the difference.
Tamago: Egg Omelet. Took me a while to get used to this. But it's just what it says it is.
Masago &
Tobiko: Roe, fish eggs. Don't count them out. They're on a lot of rolls for colour and texture and you wouldn't even know what they are if someone didn't tell you. Not much taste, but a little pop of texture that's a nice contrast to the fish.
I find beginners are more comfortable with rolls (Maki-sushi) but if you want to dive in and try the fish with rice (nigiri-sushi) or without rice (sashimi) you won't be disappointed.
(I'm sure a few more people posted in the time it took me to type this, but I hope it still helps)