So I took everyone's advice and set up 3 monitors (1 per person). Since I went with wired in-ears (I'm the drummer), I used my usual monitor for the guitarist in the middle of the front line. It definitely seemed to help them complain less, although funny enough the band was like "what do we need 3 for? We've always used 2" even though always complain they can't hear. So I think I'm going to get one more DBR10 for the front, since my monitor is also what I use for "stage volume" when I use my e-kit instead of acoustics.
I was also able to convince bassist to side fill his little amp he uses on stage, and he was next to the sub, which helped a lot as well. It was all helped by being outside so loud stage was less of an issue.