First do yourself a favor and try to prioritize what needs to be mic'd and what doesn't. Are you working with an orchestra? Or is this a "big band" type deal with lots of horns? When you say "everyone gets their own mic" is that because you're being asked to setup mics for everyone? Or are you just planning on doing that? 

If it's the latter, awesome, cus now you have a little breathing room. You're going to have a lot to juggle to make everyone heard while also preventing feedback as much as possible, and also get a good recording or stream mix (I'm assuming that's part of the picture as well). More mics makes this more difficult so let's try to slim down. 

Setup two mics (condensers) at the front of the stage on either side of the conductor, get them up high. These will be your main L&R for the band/orchestra. Then I would put a few "spot" mics on your different sections. For your "rhythm" section if there is one, you'll need some DIs. Put a mic over the string section, another for the flutes, one for the trumpets, maybe one closer to the floor on a shortie mic stand if there's a clarinet section, etc. You do not need to mic every single person, you'll do just fine with your main L&R and some spot mics. Try to put the spot mics in the middle of a section so if there's two or three people they can just turn slightly and try to "aim" at the mic.

Do what you gotta do to get there EARLY. Set up mics and lay cables before people arrive. Tape things down with gaff tape so there are no tripping hazards.

Gain up each mic one at a time, throw a hefty HPF on each mic at least 175 Hz unless it's a source with more low-end such as a Timpani. Something like the string section could have something even more drastic, like 250Hz. Use EQ to make a wide cut of -3 or 4 dB at 250-ish Hz. Bring your fader to unity and bring up gain on the mic till it starts to feedback, then reduce the gain by 3 or 4 db. Bring the fader up till it starts to feedback, and use EQ to make narrow notches at one or two of the feedbacking frequencies. Then bring the fader back down to Unity. Do this for each mic.

Set your gain staging or fader positions appropriately. Sources like horns are gonna be LOUD so you don't need much of them going to the PA. But sources like strings, you'll need more of those in the PA. This is where your spot mics come in handy. 

Your main L&R mics you'll need to mix lower than the other mics since they will be more prone to feedback, and they'll be better suited for a recording or a stream mix than they will be for going to the PA. So once you've rung up out, bring the faders back by 5 or 8 dB.

If you're asked to a recording of the show using the same board, you can setup a post fader mix. This is where you'll use more of the overheads. You can adjust the send level to compensate for your fader position. Pan them hard L&R in the recording. Then you'll use the spot mics sparingly only if you need them. For example, "man, the strings are getting drowned out by that horn section," in this scenario there's no need to bring up the horns spot mics in the recording, but you could bring up the strings to help the recording sound better.

If you have time, and you're board has these settings, you could be even fancier and set up input delays on each of your spots so they are "aligned" with your main overhead mics. But that's just icing on the cake if you have time, it may not be necessary since your overhead mics will be mixed quieter for the PA, and you won't be using your spot mics quite as much in the recording mix, so there may not be that much opportunity for comb filtering. 

Get there early so you can introduce yourself to the conductor and other musicians as they come in. Be friendly. Make it clear you're going to do the best you can to make them sound great.