While I agree that most destination weddings ARE 'selfish',
I am not so sure that this is one of them.
Personally, I would NEVER choose a destination over knowing that my mother/father/loved ones would all be able to attend.
But, to each his own.
Some may feel it is selfish to get married anywhere away from parents and immediate family. However, in the end, if the couple just wants to elope, that is their perogative.
I think that the biggest factor in being 'selfish' is being 'demanding'.... expecting everyone to bend over backwards to show up at a very high/unrealistic/prohibitive expense. (Think pricy resort....) And, I am not sure that the couple is being demanding, or that the cost is truly prohibitive. It sounds like a simple affair.
I am sorry, OP, but I just can't see what the one set of parents big 'dream vacation' has to do with this wedding.
It certainly doesn't sound like the bride is asking her mom/parents to pay for it.