don't mention wife/kids/mortgage. it is a negative for startup employment because you are bound to be the first to bail (whether by risk aversion or necessity) should things ever get tough.
You have a good point except in my case they are already aware of it since I've already been working for them for two months (and they even knew before that time).
I actually see it the other way around: if you have wife/kids/bills to pay, you're probably the LAST to jump ship, as you actually NEED the money