Re: In Laws First Visit- please help!
Honestly, I have no idea. 
The issue here is not his parents thinking you guys are losers…..its them thinking that you guys are hiding/lying something something. As mentioned earlier, its really weird not to have ANY males present when you know that the guy and his dad are coming. Especially since both your sister and cousin are actually married (it would be different if they were divorced or widowed in your situation). They are coming on a Saturday. Unless both your BIL and cousin’s husband have hourly jobs where its logical for both of them to work on a Saturday……I really dunno what excuse will reasonably explain BOTH of their absences without it coming across as a red flag.