i have never traveled with kids and bosses, its not a vacation, its work, chasing kids everywhere, think about it, Hawaii is 6 hours from San Francisco, its far, jet lag, kids screaming tired, but if you are willing then do it

It really depends on your relationship with the family. My previous MB lived in my building also so she and DH knew each other and we all got together occasionally. They would not have minded. My current NF has never met DH. Although I know he is an amazing man they don't because they also have not done a background check on him. So, even if he did fly and room separately, you should not even think about having him around their kids. Also, maybe he could come just for a few days after your finished with the family. It shouldn't cost much more if anything to come back a different day from the family or arrive a few days earlier.