I'd still give your guests the standard 6 - 8 weeks notice. You can word it in several different ways but I've worked with a lot of couples that worded it like an announcement:
"Anita and Joe were married in Maui on August 10th. Please come celebrate our union on ..."
If someone is hosting (like your parents) you should still acknowledge them:
"Mr. & Mrs. Joe Smith invite you to come celebrate the marriage of their daughter....."
"Mr & Mrs. Joe Smith would like to announce the marriage of their daughter Anna Jane to Dustin Jones. Please join us in celebrating on ..."