re: Can someone explain the “ins and outs” of inheritance tax for me?

What's a ballpark figure on total $ involved? If over the basic exclusion amount (what the poster above stated -- 5.45 million) and the deceased spousal unused exclusion (when that comes into play), you might want to take advantage of yearly untaxed gifts. For instance, your in laws could make a # of 14k per year untaxed gifts to various family members.

Above isn't legal advice. And you also have to find out what your in laws want to do with the $. I would also bring your in laws to an estate/tax attorney if the $ is significant.