Wedding invitations are an important part of the planning process for any wedding. The fact is that you absolutely need to have a master list of guests before you can even think about sending them out. Plan to gather this information first before even actually ordering invites.
Have your wedding planner help you with the process of finding the right invitations. They can help you to save money in the process and they can help you to get the invitation ordered and sent out in a timely fashion so that everyone knows about your wedding.