I would say start at dinner (maybe 6PM ish). 50mg sounds like a good place to start. Try to make a mental note of how you feel within an hour after taking it each night, and how you feel waking up in the morning (also keeping in mind how much restful sleep you got due to kid interruptions).
I can usually tell a difference within a couple of nights (falling asleep more quickly, staying asleep, less groggy in the morning) once I get the dose right. Then I start to realize that my mood/stress management is improving too.