I was always open to sex of whatever kind on first dates (or any dates, for that matter).
I always just went with the flow, and tried to read the vibes my date was sending. If I was attracted to her, and she seemed attracted to me, I never hesitated to go down on her, or to be the first to go down. Of course, I'm pretty orally-fixated!
It always just depended on how attracted we were to each other and how comfortable we were with the pace of things (mainly how comfortable SHE was, since I was usually down for whatever if I was attracted).