Im not opposed to spending money. I just don't want to be throwing it away if this band doesn't work out. I currently have no other situations where I'd be using them. As stated in my OP, my main concerns right now are blocking out anything that might trigger my tinnitus. I'm most concerned about the drums. Once I get an idea of what this is all about, and check out some of the less costly options - if the band works out for me I'll have no issues investing in whatever will work best. I'm not the type to skimp on gear. I am the type to not needlessly throw away money though.
I'm the only one in my group that has IEM and I use them whenever possible, so even if the band isn't IEM, you still can be. I don't like tinnitus, and I only have it for a day or so after a gig with no ear protection. With my 64 Audio A4's, I get a 20db cut in ambient noise, and my bass and vocals at a minimum in my ears.
Arguably with your tinnitus situation, you SHOULD ALWAYS be IEM. I run wired, not wireless, so look at it this way - the XLR that would feed a floor monitor goes to my headphone amp, and if need be, I run a line from my bass head/DI to the headphone amp as well. Everything I need, even if not every instrument is mic'd in the PA - guitars are always plenty loud, so maybe I don't have the clarity of the guitar, but I have the basic level. Not sure if you ever played the Bayou in Fleetwood/Mt. Vernon, but the stage is a postage stamp. I run IEM there because I'm right on the ride cymbal of my drummer. I take an XLR out from the old, crappy PA and my bass DI, and I have ear protection and some clarity on me and the vocals. I don't get so much kick in that situation, but I can deal with it as I have a great drummer and get plenty of hi-hat and snare ambiently. Point being, no matter the setting, you can run IEM and get the benefit, of which it is a distinct health benefit in your situation.
Given your story, I'm sort of curious as to why you didn't go IEM for yourself much earlier. Great investment in your hearing and mental sanity given the side effects of tinnitus.