I've spent a good chunk of my gaming experience with people who have small kids, and with older kids. Really, there's nothing much different.
Yes, you will have them missing games at times. Have a backup plan or game in place for those times. Have someone run their character, etc. Kids can get sick just like that (snaps fingers).
Usually, though, unless they're in the double digits they should be in bed by the time y'all are really getting started. 7-8 pm and they're usually conked out. Just be sure to be quieter than usual and you'll not hear a peep out of them.