I recommend purchasing a digital thermometer that remembers previous temperature readings. It helps me! My alarm is set to 5.30am every day, and sometimes I just go right back to sleep. It saves me having to write or remember my temp immediately, and I chart it later.
So far as the sleep option... Is there a time she usually wakes you up? The rule is really that the temperature should be taken as close to the same time of day as possible, with 3 hours of unbroken sleep. In practice, if I wake up at 4am (1 1/2 hrs early) and have to pee, I take my temp. If I go right back to sleep, I take my temp again at 5.30 and use that one. If I have trouble sleeping easily again, or if I was up for more than that odd 2 minutes, I go with the 4am temp. If I had woken up at 1 and
not gone back to sleep to get 3 unbroken hours by the time my alarm went off, I'd put a dotted line through my temps that day.
More importantly, though, is monitoring your cervical fluid. If you only follow that one, it's the one that will make or break your goal of either conception or contraception! So if you miss a few temps a month, big deal. Keep a close eye on the fluid. Toni Weschler wrote a great book on FAM. It's my fertility "bible".

Highly recommended.