whooping cough TDAP vaccine

So my husband and I are both vaccinated from whooping cough with TDAP.  I want to say something to my husbands parents about getting it, since they plan on visiting and being around right after the baby's birth.  I don't know how to approach the situation (as it seems even my husband doesn't see it as a big deal for them to get it). How many of y'all asked others to get vaccinated?? What did you say? How was it received? TIA!