Welcome, Mike.
Bandon is a favorite place of many in this group. So questions like yours have been discussed many times before... but heck, things change, so it's worth covering again. Here's my take:
1. There are eight of us (ranging from 10 - 20 handicaps) We are all taking experienced caddies, but I'm wondering if my group will benefit from yardage books as well? Do they sell yardage books at each course, or do they simply equip caddies with them and that should suffice for us? If anyone has a bunch they're interested in parting with, I'd be happy to buy them from you.
I'm a firm believer that caddies are not necessary at Bandon, and much of the time are not worth the added expense. If you've already made that decision however, then great! Go for it - they surely won't be a detriment. But there's no way you also need yardage guides if you have caddies - the courses are not THAT mysterious.
2. We are playing Bally Bandon in the middle of our Ryder Cup format tournament, partly as a break, and partly as a treat for the half of us in the group who are true architecture fans. Can anyone offer any advice in terms of format for friendly (and unorthodox) matches for eight - given that this is a very unusual course?
By this I take it you mean the Sheep Ranch site? You'll enjoy it - it is great fun. In terms of matches, the best way to do is some sort of partners thing (chapman, two man scramble, straight better ball) but make it that the winner of the hole calls what green you play to for the next hole. I know this sounds weird but it will make sense when you get there... and it will be a blast.
3. Given that our group is mixed evenly with high/low handicaps, is it a mistake for us to play the back tees on Bandon Dunes and Pac Dunes? I am reticent to mix it up, for contiguity's sake, and even the high handicaps among us are skilled golfers, just not great scorers. Will we regret not "seeing the course" from the back tees? Or is this going to be (because of the wind) like my experience at Erin Hills, where my ego caused me suffering (though I marveled at the course itself) despite the ample Black Course-like warnings to tee it up accordingly?
Wind will determine everything. If it's blowing hard, even plus handicaps wouldn't suffer from moving up a block or two... and higher cappers will get brutalized. If it's not, just wait, it will. But in any case I think ony Pacific can get too short for better players... the other two are just fine from any tee.