Destination wedding invitations have different rules from traditional wedding invitations. Normal invitations are sent out 4-6 weeks before the wedding and the reply by date is the date that your caterer needs to know numbers.
For destination weddings it is important to send the invitations a good while in advance of your wedding as those who are planning to attend will have to arrange their work schedule and travel plans. Also your travel agent may give you specific timelines and “due dates” that your guests will need to know of well in advance. It is also very important to include extra information, including a website or contact information for your travel agent.
There will be less guests for destination weddings as only those close to you will be able to attend. This does not mean you should only send invitations to those who you think can attend. You should still send invitations to all those people you would have invited if your wedding was local. This is a nice gesture, and you never know who wants to go on vacation. However make sure to let family know that there is no pressure to attend if they cannot afford to. Destination weddings can be very expensive for your guests.
Not only is sending out an invitation a nice gesture, it is also a memento for those who are unable to attend the wedding.
If you really want to include those who cannot make the trip, why not have a simple “celebration” when you get back. It does not have to be anything elaborate (as the part of the reason for destination weddings is simplicity) but even a backyard BBQ is a great way to celebrate.
Are you going to a specific destination and you want to convey that on your invitation? There are a variety of invitations available from different suppliers online including Paris wedding invitations, Mexico wedding invitations, etc.