here's a few ideas;
As someone else suggested, 2 floor moniters should be all you need.
(are you both singing?) In general, for cardiod mics, speakers should be
not be facing the buisness end of the mic directly. Some folks like small
spot moniters on mic stands at ear level. Do a search for setting up small PA. Too much to go into here.
If you are counting on getting your tone from a big guitar amp try a small amp at ear level. It sounds counter-intuitive, but a 100 watt amp is only twice as loud as a five watt amp.
Smaller drums, lighter sticks, practice pads on the heads, cymbal chokes,
lighter touch can help with drum volume.
Are you learning and practicing arrangments or just jamming.
If it's the former, you really don't need much volume at all.
I practice in a guitar/drums duo with a 50 watt PA. Never turned it more than halfway up.
Here's another thing i've done. Run your 2 mics into the mixer, run your guitar through a modeler (pod, microcube, sans amp, etc.),
Put the drummer on electronic drums ( i have a cheap yamaha unit ($100 used),mute the speakers and moniter on headphones.
Don't laugh, it works great!
bye the way, jumping up and down and yelling is ok too, you know.
Just watch your eardrums.