Most families don't always do *everything* together, for obvious reasons. Take a nursing baby on a 2-week motorcycle trip? No way!
There's other ways to give deserved time to a child than such extended exclusive attention.
Two weeks, out of an entire life? Not a great deprivation for the rest of the family, imo, and a HUGE event (I assume) to the 18-year-old in question. Don't you think the mother and younger girls said, "Great! Y'all have a nice time!" and planned activities that they would enjoy together in the absence of the father and teenager? That's what I would do. Having the 18-year-old out of the house for a while could be as much a reward for the mother and siblings as the trip would be for the daughter!
Perhaps the other children will get two-week trips with their Dad when they're older. Usually some family members have an interest that others don't. I couldn't go on a motorcycle trip, if (hypothetically), my husband had decided to take our 18-year-old on such an excursion. (I swore a blood oath to OldTax-lady that I'd never ride a motorcycle. Long story.) And it's understood, at least in my family, that older children get to do some things younger ones don't. Bill (15) gets to go on trips for marathon races; James (5) doesn't. The younger children will have experiences the older ones didn't, including their own rooms and no babies in the house, at some point!
It's thoughtful of you to be concerned about everyone's feelings, but families have different levels of all-togetherness that suit them
To be honest, I think the people speculating about impropriety simply have filthy minds, and if I knew them, I'd try to do something to shock them on a regular basis, just for kicks.
In this family, two are HS age and the other just short of it. Also, the younger two have made decidedly unhappy remarks to my wife about it. These are people who never go anywhere on vacation. But now when one becomes possible...
And now I'm getting into specifics far more than I intended. I know you're trying to paint reasons why this isn't that unusual, but for this family it was. And, being something I wouldn't do unless the family was involved (when I went camping with the kids, they all went), I thought it worth commenting on. Thanks for your input.
“To be honest, I think the people speculating about impropriety simply have filthy minds, and if I knew them, I’d try to do something to shock them on a regular basis, just for kicks”
I was thinking the same thing.
That was exactly my thought and I'd get great pleasure doing things to shock them too...LOL.