Is delaying prayer beyond its prescribed time due to the nature of nighttime work and sleeping during the day considered a legitimate excuse in Islamic law, or is that regarded as a dereliction in performing prayer on time?

If you perform every prayer before its time expires, you are not delaying it, because the prayer time is extended. As for congregational prayer, it is obligatory according to the more preponderant opinion. So, if you are able to pray with some of your family, then do so. If you do not find anyone to pray with in congregation and you are excused due to your need for sleep, there is no sin upon you for missing the congregation. One who is overcome by drowsiness and fears missing the prayer is excused from attending the congregation.