WOOOOOOOOT!!!
I got up early this morning and thought "just check them all again to start off the day". I got a room!!! We'll be in the Rainbow for three nights, and I am so excited!
If anyone out there is still looking, here's the trick I found--- the three casinos in West Wendover don't allow sites like Kayak to include their information in the listings. You actually have to go to the website
https://reserve1.peppermillcas.com/cgi-bin/lansaweb?PROCFUN+RN+resnet+WR1+funcparms+UP(A2560):;;?/ which covers Peppermill, Rainbow, and Monteray Bay, and manually search every day for availability. For newbies coming in like myself, it initially didn't occur to me that when I searched Kayak.com and the other sites, those three weren't listed anywhere. Click on "Speed Week Packages", then Check Rates, for EACH of the three hotels (icons at the bottom). I've been doing that for weeks and it paid off this morning.
After I booked, I called in person and asked a few questions to make sure they had my reservation, everything was secure, etc.
Many thanks to everyone who has encouraged me and tried to help us find a spot. It all worked out in the end. It's going to end up being a significant expense, but no more worry about driving two hours each way and next time we'll be able to book earlier!
GreyCrazy