For a venue and audience that size, the most important thing will be making the vocals audible. You should run mono. If you don’t have even small subs then bass and kick drum might not make sense to run through the PA at all.
- Vocal mikes up on channels 1-3
- Channel 4 mono keyboards channel (a passive DI with ground lift would be ideal for this)
- Kick drum mic on channel 5/6
- bass DI (ideally a DI out from a bass amp) on 7/8
- guitar 1 miked on channels 9/10,
- guitar 2 miked on channels 11/12
How I would mix it:
Being the vocals up to unity on their channels, maybe drop BG vox a little - 3-6 dB. Bring the main fader up until the vox are clearly audible over the band. If you can’t get them audible you PA is too small or you have something configured wrong with the front of house rig.
Once that’s done, you have the minimum requirements for a show met. Likely the keyboards might be hard to hear. If so, bring them up, starting about halfway up until they sit under the vocals and maybe just slightly quieter than the stage sound from the bass amp. EQ the keys to sit as best you can.
Once that’s done, you might want to do something similar with the guitars. Their stage sound will probably be louder than the key stage sound so they need less in the PA. I’d bring them up slowly from nothing until I can just barely tell they are in the PA. Cut the lows pretty hard on these channels and maybe roll the highs off a little since a mic right on a speaker cone can be harsh.
Now, if you have subs for FOH, I’d bring the kick drum in just a little and boost the low EQ on that channel just a little. This is another case of bring it up until you can just barely tell. Kick drum similar but only if it sounds quieter than the snare and just bring it up to match the snare and give it thump.
If you have no subs at FOH, then the most you can add for kick and bass is some articulation. Without subs if you try to boost lows on kick and bass into the PA you will easily take up all the power bandwidth for vocals and the singers will be lost. Unless you have some mixing experience - enough so that you probably wouldn’t need to ask this question, I would resist the urge to put any kick or bass in the PA if you have no subs. Having the bass DI in the PA is good if there’s a problem with the bass amp but again you gotta be very careful not to bury everything else and make the PA into a huge bass amp.
Overall, if the keyboard and bass players have decent amps, you often don’t need a PA for anything but vocals under 200 audience members. I suggest keeping that in mind as you do this. The PA is for the vocals because they have no other way to get heard. If if you have a lot of watts and headroom out front (maybe 1500 - 2000+), then you have more leeway to augment the other instruments. Otherwise, whatever you do with non-vox is going to take some away from the vox, so only if you need it and as little as necessary.
Regarding your continued desire to put drums besides kick in the PA:
A) You don't need to. Unless you're outdoors in an open field and even then you probably don't need to.
B) At 225 Watts per, for a total of 450 Watts, you're definitely in "vocals only" territory.
Aside from maybe the kick drum, indoors in front of <200 people you do not need drums in the PA. If people can't hear the drums either you have accidentally gotten a jazz drummer in your high energy rock band or your guitar and/or bass amps are way too loud. And if those amps are too loud, people are going to more likely complain about not hearing the vocals.
Let's look at your actual biggest problem, which has nothing to do with drums:
Suppose you have two guitar amps that are rated at 30-50 Watts and a bass amp rated at 100 watts (those are conservative numbers). The guitar amps will probably have distortion for at least some parts of the show and otherwise do not need or use headroom so when comparing with a PA and vocals they kind of "count" for double, so that's effectively 100 watts for each guitar. The bass might play compressed and/or with a little distortion so they are maybe comparable at 1.5 times the rated output so lets call that 150 Watts.
So you're looking at a phantom "350 Watt PA" for guitars and bass and only a real 450 Watt PA for three singers and keyboards. Add in the acoustic Watts of the drum kit and you're in for a rough ride.
Ideally the keyboard player would get an amp and leave you maximum wattage for vocals, because you're going to need them.
If you're doing band practices you should set some of this up at band practice. If you can get the monitors working for vocals and keys at band practice and hear them over drums, guitars, and bass, then you'll have clues about how to do FOH also.
If you try to put overheads through the PA, crash cymbals and open high hat will make everything completely inaudible unless you have a huge stage, a huge venue, and a professional mix engineer. Keep in mind that all of your vocal mikes are also mid-field drum room mikes. Making the snare and cymbals audible is absolutely your lowest, lowest concern here. With three open vocal mikes on stage and some stages being so small there's no room for a bass amp, you're already miking the drum kit more than anything else.