Crazy Pineapple is the first mixed game every group that's reluctantly testing the waters should play. If they like that, try Three-Hand Hold'em next - it gives them
more options and
two discards. Either way, try Double-Board Hold'em next, so they can learn about split pots.
Hollywood is a simple variation that adds some spice - it's like Pineapple, but they get to keep the extra card instead of discarding it, but the extra card is publicly visible.
I'd encourage you to try 2-7 Triple Draw; it gets them interested in draw games and it's super-easy to understand and a lot of fun to play. It also gets them into low games, which will help when it's time to play Omaha 8 or Razz.
No-limit Single Draw is as simple a game as exists. It's the granddaddy of all poker; everyone knows how to play it, but it's a little dry. Play it with deuces wild to make it more interesting.
If they enjoy the draw games and enjoy the discarding games (Pineapple and Three-Hand Hold'em) then you could try Scrotum aka Holdout. It seems like a really weird game at first, but conceptually it's just five-card draw combined with a community board and is pretty easy to grasp when it's explained that way.
Stud is great, but don't start with any stud games; it's sufficiently different that hold'em players will get confused and frustrated if they're not already enthusiastic about trying new things.
For a game that's
structurally the same as Hold'em but
strategically different, try Showtime and Encore. It takes the additional-public-information gameplay aspect from Stud and adds it to Hold'em:
Showtime: Hold’em, mucked cards are mucked face-up.
Encore: After the Showtime hand is complete, turn the muck face-down and immediately deal a new hand using only the stub from the first hand, without moving the button. The winner of the first hand posts a big blind and betting proceeds to the left of the winner. No other blinds or antes are posted. Later betting rounds start to the left of the button as usual. Mucked cards are mucked face-down as usual.
If they play a few of these and decide they like mixed games, have them try Omaha the next time you play, and devote the whole night to it so that they can practice practice practice getting their mind around it. Don't jump into any Omaha variations until they're all super-excited about playing just plain Omaha. But once you get there you can teach them anything, including Stud and Razz.
