We're at a conference the week prior, and I booked a stay from Nov 4th departing the 8th way back in March or April or something, just in case. I sure was glad I did - Saturday the 4th disappeared shortly thereafter for all the hotels I wanted, likely due to the FW 1/2 marathon.
Oddly, when I type in your dates, I get nothing for the 9th-12th (OK, VGF, but that's it), but when I look for 9th-11th and then 11th-12th, there is a lot of choice - including stays at the same rate at the same hotel(s). I saw that this has been happening with online booking. If I were you, I'd call or book them separately and then call to see if they can be combined. Good luck.