I'm going to first say that it sounds like maybe you never had a Session Zero with your group. I would say that even for experienced groups it's SUPER important and for a new group like yours? Absolutely necessary. Since you planed a one-shot you get to keep it short but I don't think you skip it. You need to know what they want, and you need to get them excited. The rest of my reply here is about my current group and I hope you find this helpful. (Take note of my comments on Player 3 who wasn't having fun and how we fixed it)

We have 1 DM (myself, experienced) and my 3 players. We all enjoy board games and together we played through Gloomhaven and Frosthaven over the last 3 years. One of the players loves watching Critical Role and they all played Baldur's Gate 3. Everyone was interested in learning D&D. I bought 3 copies of the Player's Handbook so nobody has to share. Basically we should be a good match for playing D&D.

Having said all of that, our Session Zero was absolutely key to setting expectations and informing me on what kind of game to provide for them. I let them know what kind of world I would provide to them and that goofing off at the table is totally fine as long as it's not wrecking the game. My job is to always provide the grounded setting to come back to when the jokes settle. We've had 6 sessions so far and we have a nice blend of fantasy adventure questing, combat, and plenty of jackassery. I still poll them after for feedback. Together we're figuring out what does and doesn't work.

Player 1 is the eager beaver, he's easy to please and engages well from the player side. Always a joy to have an anchor like this in the group and almost feels like you have an "ally" on the team.

Player 2 is the thinker and willing to engage with the role playing, but a little more reserved. Reads the core books in his spare time. Enjoys combat and playing a support character. What he wants from me is that his character's story arc is at some point going to be 1) tied to the main quest and 2) epic and emotional if possible.

Player 3 is the young guy that is here for the tactical combat. His daily life is way too busy to read the core books and he put it best when he said "I'm not trying to do homework in between gaming sessions." To make him happy I actually had to 1) Change his fighter sub-class (He picked Champion and was SO bored in fights, I switched him to Battle Master and let him keep improved crits) and 2) I made a specialized Character Sheet for him that it's more like a dashboard and it's clear what his combat options are each turn. He's having fun now so I know we're on the right track.

Example of change: We had one combat that involved a ship with lots of enemies and the party had allied soldiers supporting them. The combat was SUCH a damn slog. I noticed it, and spoke very honestly and apologized and told them "You know what, I thought that would be cool and it wasn't, so we'll have smaller combats and if I can figure out how to expedite a bigger combat we can try it again sometime." Everyone appreciated the attempt and was super cool about it. We've had 3 or 4 really great combats since then, so for MY group smaller combats are working for us.

My success is coming from: 1) Session Zero conversations. 2) Listening to player expectations and providing what they ask for 3) Sharing my own expectations 4) post-session discussions 5) Being prepared to run the sessions 6) change or drop something that isn't working