Okay, are you ready to hear from Sarah aka Emily Post?
Etiquette demands that you make no mention of gifts whatsoever on invitations to formal events such as weddings. Period. No ifs ands or buts.
What should take place, is that those invited to said events are presumed to be close enough to family members (such as yourself, siblings, mother of the groom, etc) that they will ask: "where is DD registered for gifts?" or "what should we get them?".
At that time (and only at that time) the kind guest can be told that the young couple are planning a move to Brazil immediately following the wedding and have thus chosen not to register for gifts that would be difficult to ship to South America.
It is up to you, and other family members, to decide if you are close enough to the person asking, and they are amenable to the suggestion, that they give a monetary gift. Otherwise you should just say that their presence at the wedding will be a wonderful gift to the couple.
In many cultures, money is given at the wedding to the groom (even in our very southern and non-money giving culture, we still got around $500 handed over in cash to DH) for the honeymoon.
It is positively tacky to include solicitation for gifts of any kind on an invitation, even with the very best of intentions. A gracious bride does not expect anything from invited guests but their attendance.