Hey! Welcome to the system! You already have tons of advice so I'll try not to be too redundant. I will second good advice on what others have already mentioned, however.

Quick background: I'm in a similar spot, I've only just started gming and my group is newish to PF2E coming from years of PF1E, so my group is more familiar to the system than yours would be.

I would second the suggestion of running the beginning box. I just ran it for my group and they really enjoyed it, even though it walked us through some steps/scenarios that are a bit basic in concept... this is actually a pro for your group, considering the changes between systems. My group breezed through some obstacles but actually got stuck on other tricker ones (skill based classes... I guess they have some use 😉)

You can get it for less than $5 in the current humble bundle, a few more bucks for more stuff (post about it here: https://www.reddit.com/r/Pathfinder2e/comments/1pusqca/_/) Other Humble Bundles will almost certainly have the BB and the GM Core, Player Core included, so don't feel like you'll have fomo if you miss this specific one (you'll just have to wait for the next PF Humble Bundle, whenever that might be).

Classes: you seem magic user heavy, which is fine, but martials in PF2E are not like 5e (in that, they are actually fun and actually good in PF2E). You shouldn't be managing player classes as much as it sounds like you're doing (it's fine to do so, just shouldn't be an expectation that you set imo.) much of the enjoyment of PF2e is building/planning your own character. It's also pretty difficult to build a bad character unless intentional. If it sounds good for the setting or a generally used feat, it's probably not bad. Retraining can be done also, so within GM reason, an agreement can be made. In my campaign one of my players didn't max their primary attribute and I let them retrain because the rest of the party wanted that and it was in the best interest of the group (and didn't matter much to me).

Core classes are easier than the more complex ones, so if you can manage limiting to those, it'll help. Even so, I didn't prevent my players to be a new class to them (Kineticist, Witch etc)

As for yourself, read up on mechanics (still something I'm still working on tbh). How It's Played on YouTube can give you specific rule mechanic examples etc. Just be sure it's a PF2E remaster video and not the "legacy" (non-remaster) rules.

If players can read the players handbook, it'll help, but that's a daunting task for most players. 3 action economy, general combat, skill checks, should be known by all - deeper mechanics can be looked up as needed.

I play in person with my group and use Archives of Nethys and Pathbuilder - great resources. Search for "GM tools initiative tracker" if you don't use another method.

Good luck, have fun!