Personally, i would go for a morning weigh in, and the same day and time (and clothes) each week.
Mine are evening weigh in's and i really dont like them.
As long as u getting weighed similar times each week it shouldn't matter i always weigh in on evening too cos of work but always wear same clothes never affected me last time hoping it wont this time either
Whatever time you choose try to stick with it. I have done both evening and morning ones but I prefer morning as I don't feel that weird pressure not eat/drink properly throughout the day like I do when I have an evening WI.