It is not really "his" decision, it is clearly hers as well. I am sure that if your daughter didn't want to get married elsewhere, she would have said. I don't think he is "exploiting" anything - they have obviously discussed it. Perhaps knowing she doesn't want any fuss, this is why he has suggested it. Reading between the lines on your post, you do seem to have rather taken against your daughter's fiance in all this. Remember your words in the second paragraph "she's very happy with him".
on the one hand, I can really understand that you would like to be there. On the other hand, it is their day. Having been married once and doing what everyone else wanted rather than what I wanted, I will do things differently next time.
It might help to build bridges if you say how happy you are for them and perhaps later on, if their plans go ahead, suggest a small family party to celebrate the union on their return? I know it will be difficult, but if you could put your feelings about not being there aside, and listen to your daughter with excitement about her plans, it might help?