We had a 5am flight out and traveling with the kids. The only option for us was to book the Marriott at IAH. The girl that checked us in was phenomenal - so helpful - I only wish I remembered her name. The lobby/bar/restaurant is very nicely done. The rooms are small, but comfy. Best attribute (and surprise) was how quiet the room was considering how close we are to the airport.
The hotel is situated between Terminals A/B and C/D/E with lifts that go directly down to the internal underground train - very easy walk.
If you have a crack-of-dawn flight this would be the easiest way with kids-in-tow to get everyone to the flight on time.More